diff --git a/backend/alembic/versions/20260224_drop_profile_display_name_and_trigger_username.py b/backend/alembic/versions/20260224_drop_profile_display_name_and_trigger_username.py
new file mode 100644
index 0000000..503888b
--- /dev/null
+++ b/backend/alembic/versions/20260224_drop_profile_display_name_and_trigger_username.py
@@ -0,0 +1,121 @@
+"""drop_profile_display_name_and_trigger_username
+
+Revision ID: 20260224_drop_profile
+Revises: 20260224_bind_profiles_auth
+Create Date: 2026-02-24 22:10:00.000000
+
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+
+
+revision: str = "20260224_drop_profile"
+down_revision: Union[str, Sequence[str], None] = "20260224_bind_profiles_auth"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.execute(
+        """
+        ALTER TABLE public.profiles
+        DROP CONSTRAINT IF EXISTS uq_profiles_username
+        """
+    )
+
+    op.execute(
+        """
+        ALTER TABLE public.profiles
+        DROP COLUMN IF EXISTS display_name
+        """
+    )
+
+    op.execute(
+        """
+        CREATE OR REPLACE FUNCTION public.create_profile_for_new_user()
+        RETURNS trigger
+        LANGUAGE plpgsql
+        SECURITY DEFINER
+        SET search_path = public
+        AS $$
+        BEGIN
+            INSERT INTO public.profiles (id, username)
+            VALUES (
+                NEW.id,
+                COALESCE(
+                    NULLIF(NEW.raw_user_meta_data->>'username', ''),
+                    'user_' || substr(replace(NEW.id::text, '-', ''), 1, 25)
+                )
+            )
+            ON CONFLICT (id) DO NOTHING;
+
+            RETURN NEW;
+        END;
+        $$
+        """
+    )
+
+
+def downgrade() -> None:
+    op.execute(
+        """
+        ALTER TABLE public.profiles
+        ADD COLUMN IF NOT EXISTS display_name VARCHAR(50)
+        """
+    )
+
+    op.execute(
+        """
+        WITH ranked AS (
+            SELECT
+                id,
+                username,
+                row_number() OVER (
+                    PARTITION BY username
+                    ORDER BY created_at ASC, id ASC
+                ) AS rn
+            FROM public.profiles
+            WHERE username IS NOT NULL
+        )
+        UPDATE public.profiles p
+        SET username = LEFT(p.username, 24) || '_' || (ranked.rn - 1)::text
+        FROM ranked
+        WHERE p.id = ranked.id
+          AND ranked.rn > 1
+        """
+    )
+
+    op.execute(
+        """
+        ALTER TABLE public.profiles
+        ADD CONSTRAINT uq_profiles_username UNIQUE (username)
+        """
+    )
+
+    op.execute(
+        """
+        CREATE OR REPLACE FUNCTION public.create_profile_for_new_user()
+        RETURNS trigger
+        LANGUAGE plpgsql
+        SECURITY DEFINER
+        SET search_path = public
+        AS $$
+        BEGIN
+            INSERT INTO public.profiles (id, username, display_name)
+            VALUES (
+                NEW.id,
+                'user_' || substr(replace(NEW.id::text, '-', ''), 1, 25),
+                COALESCE(
+                    NULLIF(NEW.raw_user_meta_data->>'display_name', ''),
+                    NULLIF(NEW.raw_user_meta_data->>'full_name', '')
+                )
+            )
+            ON CONFLICT (id) DO NOTHING;
+
+            RETURN NEW;
+        END;
+        $$
+        """
+    )
diff --git a/backend/src/core/auth/models.py b/backend/src/core/auth/models.py
index f0ee9ea..f7a31d5 100644
--- a/backend/src/core/auth/models.py
+++ b/backend/src/core/auth/models.py
@@ -7,3 +7,5 @@ from uuid import UUID
 @dataclass(frozen=True)
 class CurrentUser:
     id: UUID
+    email: str | None = None
+    role: str | None = None
diff --git a/backend/src/models/profile.py b/backend/src/models/profile.py
index f4d1cb6..d903c20 100644
--- a/backend/src/models/profile.py
+++ b/backend/src/models/profile.py
@@ -26,14 +26,9 @@ class Profile(TimestampMixin, SoftDeleteMixin, Base):
     )
     username: Mapped[str] = mapped_column(
         String(30),
-        unique=True,
         nullable=False,
         index=True,
     )
-    display_name: Mapped[str | None] = mapped_column(
-        String(50),
-        nullable=True,
-    )
     avatar_url: Mapped[str | None] = mapped_column(
         Text,
         nullable=True,
diff --git a/backend/src/v1/auth/dependencies.py b/backend/src/v1/auth/dependencies.py
index 46b54b8..7de951e 100644
--- a/backend/src/v1/auth/dependencies.py
+++ b/backend/src/v1/auth/dependencies.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
-from v1.auth.service import AuthService, SupabaseAuthGateway
+from v1.auth.gateway import SupabaseAuthGateway
+from v1.auth.service import AuthService
 
 
 def get_auth_service() -> AuthService:
diff --git a/backend/src/v1/auth/gateway.py b/backend/src/v1/auth/gateway.py
new file mode 100644
index 0000000..a003bc3
--- /dev/null
+++ b/backend/src/v1/auth/gateway.py
@@ -0,0 +1,154 @@
+from __future__ import annotations
+
+import asyncio
+from typing import Any, cast
+
+from fastapi import HTTPException
+from supabase import AuthError, create_client
+
+from core.config.settings import SupabaseSettings, config
+from core.logging import get_logger
+from v1.auth.schemas import (
+    AuthTokenResponse,
+    AuthUser,
+    AuthUserByEmailResponse,
+    LoginRequest,
+    RefreshRequest,
+    SignupRequest,
+)
+from v1.auth.service import AuthServiceGateway
+
+logger = get_logger("v1.auth.gateway")
+
+
+class SupabaseAuthGateway(AuthServiceGateway):
+    _client: Any
+    _admin_client: Any
+
+    def __init__(self) -> None:
+        settings: SupabaseSettings = config.supabase
+        self._client = create_client(settings.url, settings.anon_key)
+        self._admin_client = create_client(settings.url, settings.service_role_key)
+
+    async def signup(self, request: SignupRequest) -> AuthTokenResponse:
+        payload: dict[str, Any] = {
+            "email": request.email,
+            "password": request.password,
+            "data": {"username": request.username},
+        }
+        try:
+            sign_up = cast(Any, self._client.auth.sign_up)
+            response = await asyncio.to_thread(sign_up, payload)
+            return _map_auth_response(response, "Authentication failed")
+        except AuthError as exc:
+            logger.warning("Signup failed", error_type=type(exc).__name__)
+            raise HTTPException(
+                status_code=401, detail="Authentication failed"
+            ) from exc
+
+    async def login(self, request: LoginRequest) -> AuthTokenResponse:
+        payload: dict[str, Any] = {"email": request.email, "password": request.password}
+        try:
+            sign_in = cast(Any, self._client.auth.sign_in_with_password)
+            response = await asyncio.to_thread(sign_in, payload)
+            return _map_auth_response(response, "Invalid credentials")
+        except AuthError as exc:
+            logger.warning("Login failed", error_type=type(exc).__name__)
+            raise HTTPException(status_code=401, detail="Invalid credentials") from exc
+
+    async def refresh(self, request: RefreshRequest) -> AuthTokenResponse:
+        try:
+            response = await asyncio.to_thread(
+                self._client.auth.refresh_session,
+                request.refresh_token,
+            )
+            return _map_auth_response(response, "Invalid refresh token")
+        except AuthError as exc:
+            logger.warning("Refresh failed", error_type=type(exc).__name__)
+            raise HTTPException(
+                status_code=401, detail="Invalid refresh token"
+            ) from exc
+
+    async def logout(self, refresh_token: str | None) -> None:
+        if not refresh_token:
+            raise HTTPException(status_code=401, detail="Missing refresh token")
+        try:
+            response = await asyncio.to_thread(
+                self._client.auth.refresh_session,
+                refresh_token,
+            )
+            session = getattr(response, "session", None)
+            if session is None:
+                raise HTTPException(status_code=401, detail="Invalid refresh token")
+            await asyncio.to_thread(
+                self._client.auth.set_session,
+                str(session.access_token),
+                str(session.refresh_token),
+            )
+            await asyncio.to_thread(self._client.auth.sign_out)
+        except AuthError as exc:
+            logger.warning("Logout failed", error_type=type(exc).__name__)
+            raise HTTPException(
+                status_code=401, detail="Invalid refresh token"
+            ) from exc
+
+    async def get_user_by_email(self, email: str) -> AuthUserByEmailResponse:
+        users = await asyncio.to_thread(_list_auth_users, self._admin_client)
+        normalized_email = email.lower()
+        user = next(
+            (
+                candidate
+                for candidate in users
+                if str(getattr(candidate, "email", "")).lower() == normalized_email
+            ),
+            None,
+        )
+        if user is None:
+            raise HTTPException(status_code=404, detail="User not found")
+
+        return AuthUserByEmailResponse(
+            id=str(getattr(user, "id", "")),
+            email=str(getattr(user, "email", "")),
+            created_at=str(getattr(user, "created_at", "")),
+            email_confirmed_at=(
+                str(getattr(user, "email_confirmed_at", ""))
+                if getattr(user, "email_confirmed_at", None)
+                else None
+            ),
+        )
+
+
+def _map_auth_response(response: object, failure_message: str) -> AuthTokenResponse:
+    session = getattr(response, "session", None)
+    user = getattr(response, "user", None)
+    if session is None or user is None:
+        raise HTTPException(status_code=401, detail=failure_message)
+
+    email = getattr(user, "email", None)
+    if not email:
+        raise HTTPException(status_code=401, detail=failure_message)
+
+    auth_user = AuthUser(id=str(user.id), email=str(email))
+    return AuthTokenResponse(
+        access_token=str(session.access_token),
+        refresh_token=str(session.refresh_token),
+        expires_in=int(session.expires_in or 0),
+        token_type=str(session.token_type),
+        user=auth_user,
+    )
+
+
+def _list_auth_users(client: Any) -> list[Any]:
+    users: list[Any] = []
+    page = 1
+
+    while True:
+        response = client.auth.admin.list_users(page=page, per_page=100)
+        batch = list(getattr(response, "users", []))
+        users.extend(batch)
+
+        if len(batch) < 100:
+            break
+        page += 1
+
+    return users
diff --git a/backend/src/v1/auth/router.py b/backend/src/v1/auth/router.py
index 4ee6599..05067be 100644
--- a/backend/src/v1/auth/router.py
+++ b/backend/src/v1/auth/router.py
@@ -1,10 +1,16 @@
 from __future__ import annotations
 
-from fastapi import APIRouter, Depends, Response
+from typing import Annotated
 
+from fastapi import APIRouter, Depends, Response
+from fastapi import HTTPException
+
+from core.auth.models import CurrentUser
 from v1.auth.dependencies import get_auth_service
+from v1.profile.dependencies import get_current_user
 from v1.auth.schemas import (
     AuthTokenResponse,
+    AuthUserByEmailResponse,
     LoginRequest,
     LogoutRequest,
     RefreshRequest,
@@ -47,3 +53,14 @@ async def logout(
 ) -> Response:
     await service.logout(payload.refresh_token)
     return Response(status_code=204)
+
+
+@router.get("/users/by-email", response_model=AuthUserByEmailResponse)
+async def get_user_by_email(
+    email: str,
+    current_user: Annotated[CurrentUser, Depends(get_current_user)],
+    service: AuthService = Depends(get_auth_service),
+) -> AuthUserByEmailResponse:
+    if current_user.role != "service_role" and current_user.email != email:
+        raise HTTPException(status_code=403, detail="Forbidden")
+    return await service.get_user_by_email(email)
diff --git a/backend/src/v1/auth/schemas.py b/backend/src/v1/auth/schemas.py
index 958c979..fbf37fd 100644
--- a/backend/src/v1/auth/schemas.py
+++ b/backend/src/v1/auth/schemas.py
@@ -6,9 +6,9 @@ from pydantic import BaseModel, EmailStr, Field
 
 
 class SignupRequest(BaseModel):
+    username: str = Field(min_length=3, max_length=30)
     email: EmailStr
     password: str = Field(min_length=6)
-    display_name: str | None = None
     redirect_to: str | None = None
 
 
@@ -38,6 +38,13 @@ class AuthTokenResponse(BaseModel):
     user: AuthUser
 
 
+class AuthUserByEmailResponse(BaseModel):
+    id: str
+    email: EmailStr
+    created_at: str
+    email_confirmed_at: str | None = None
+
+
 class SignupPendingResponse(BaseModel):
     status: Literal["pending_verification"] = "pending_verification"
     user: AuthUser
diff --git a/backend/src/v1/auth/service.py b/backend/src/v1/auth/service.py
index 3217eaf..6d5a7e3 100644
--- a/backend/src/v1/auth/service.py
+++ b/backend/src/v1/auth/service.py
@@ -1,25 +1,16 @@
 from __future__ import annotations
 
-import asyncio
-from typing import Any, Protocol, cast
+from typing import Protocol
 
-from fastapi import HTTPException
-from supabase import AuthError, create_client
-
-from core.config.settings import SupabaseSettings, config
-from core.logging import get_logger
 from v1.auth.schemas import (
     AuthTokenResponse,
-    AuthUser,
+    AuthUserByEmailResponse,
     LoginRequest,
     RefreshRequest,
     SignupRequest,
 )
 
 
-logger = get_logger("v1.auth.service")
-
-
 class AuthServiceGateway(Protocol):
     async def signup(self, request: SignupRequest) -> AuthTokenResponse:
         raise NotImplementedError
@@ -33,79 +24,8 @@ class AuthServiceGateway(Protocol):
     async def logout(self, refresh_token: str | None) -> None:
         raise NotImplementedError
 
-
-class SupabaseAuthGateway(AuthServiceGateway):
-    _client: Any
-
-    def __init__(self) -> None:
-        settings: SupabaseSettings = config.supabase
-        self._client = create_client(settings.url, settings.anon_key)
-
-    async def signup(self, request: SignupRequest) -> AuthTokenResponse:
-        payload: dict[str, Any] = {
-            "email": request.email,
-            "password": request.password,
-        }
-        if request.display_name:
-            payload = {
-                **payload,
-                "data": {"display_name": request.display_name},
-            }
-        try:
-            sign_up = cast(Any, self._client.auth.sign_up)
-            response = await asyncio.to_thread(sign_up, payload)
-            return _map_auth_response(response, "Authentication failed")
-        except AuthError as exc:
-            logger.warning("Signup failed", error=str(exc))
-            raise HTTPException(
-                status_code=401, detail="Authentication failed"
-            ) from exc
-
-    async def login(self, request: LoginRequest) -> AuthTokenResponse:
-        payload: dict[str, Any] = {"email": request.email, "password": request.password}
-        try:
-            sign_in = cast(Any, self._client.auth.sign_in_with_password)
-            response = await asyncio.to_thread(sign_in, payload)
-            return _map_auth_response(response, "Invalid credentials")
-        except AuthError as exc:
-            logger.warning("Login failed", error=str(exc))
-            raise HTTPException(status_code=401, detail="Invalid credentials") from exc
-
-    async def refresh(self, request: RefreshRequest) -> AuthTokenResponse:
-        try:
-            response = await asyncio.to_thread(
-                self._client.auth.refresh_session,
-                request.refresh_token,
-            )
-            return _map_auth_response(response, "Invalid refresh token")
-        except AuthError as exc:
-            logger.warning("Refresh failed", error=str(exc))
-            raise HTTPException(
-                status_code=401, detail="Invalid refresh token"
-            ) from exc
-
-    async def logout(self, refresh_token: str | None) -> None:
-        if not refresh_token:
-            raise HTTPException(status_code=401, detail="Missing refresh token")
-        try:
-            response = await asyncio.to_thread(
-                self._client.auth.refresh_session,
-                refresh_token,
-            )
-            session = getattr(response, "session", None)
-            if session is None:
-                raise HTTPException(status_code=401, detail="Invalid refresh token")
-            await asyncio.to_thread(
-                self._client.auth.set_session,
-                str(session.access_token),
-                str(session.refresh_token),
-            )
-            await asyncio.to_thread(self._client.auth.sign_out)
-        except AuthError as exc:
-            logger.warning("Logout failed", error=str(exc))
-            raise HTTPException(
-                status_code=401, detail="Invalid refresh token"
-            ) from exc
+    async def get_user_by_email(self, email: str) -> AuthUserByEmailResponse:
+        raise NotImplementedError
 
 
 class AuthService:
@@ -126,22 +46,5 @@ class AuthService:
     async def logout(self, refresh_token: str | None) -> None:
         await self._gateway.logout(refresh_token)
 
-
-def _map_auth_response(response: object, failure_message: str) -> AuthTokenResponse:
-    session = getattr(response, "session", None)
-    user = getattr(response, "user", None)
-    if session is None or user is None:
-        raise HTTPException(status_code=401, detail=failure_message)
-
-    email = getattr(user, "email", None)
-    if not email:
-        raise HTTPException(status_code=401, detail=failure_message)
-
-    auth_user = AuthUser(id=str(user.id), email=str(email))
-    return AuthTokenResponse(
-        access_token=str(session.access_token),
-        refresh_token=str(session.refresh_token),
-        expires_in=int(session.expires_in or 0),
-        token_type=str(session.token_type),
-        user=auth_user,
-    )
+    async def get_user_by_email(self, email: str) -> AuthUserByEmailResponse:
+        return await self._gateway.get_user_by_email(email)
diff --git a/backend/src/v1/profile/dependencies.py b/backend/src/v1/profile/dependencies.py
index 9088e71..8a4536f 100644
--- a/backend/src/v1/profile/dependencies.py
+++ b/backend/src/v1/profile/dependencies.py
@@ -82,7 +82,9 @@ def get_current_user(authorization: str | None = Header(default=None)) -> Curren
         raise HTTPException(status_code=401, detail="Unauthorized")
 
     logger.debug("JWT validation successful", user_id=str(user_id))
-    return CurrentUser(id=user_id)
+    email = payload.get("email") if isinstance(payload.get("email"), str) else None
+    role = payload.get("role") if isinstance(payload.get("role"), str) else None
+    return CurrentUser(id=user_id, email=email, role=role)
 
 
 def get_profile_service(
diff --git a/backend/src/v1/profile/repository.py b/backend/src/v1/profile/repository.py
index faaffa8..253027f 100644
--- a/backend/src/v1/profile/repository.py
+++ b/backend/src/v1/profile/repository.py
@@ -3,6 +3,7 @@ from __future__ import annotations
 from typing import TYPE_CHECKING, Protocol
 from uuid import UUID
 
+from sqlalchemy import select
 from sqlalchemy.exc import SQLAlchemyError
 
 from core.db.base_repository import BaseRepository
@@ -54,7 +55,15 @@ class SQLAlchemyProfileRepository(BaseRepository[Profile]):
 
     async def get_by_username(self, username: str) -> Profile | None:
         try:
-            return await self.get_one(Profile.username == username)
+            stmt = (
+                select(Profile)
+                .where(Profile.username == username)
+                .where(Profile.deleted_at.is_(None))
+                .order_by(Profile.created_at.asc())
+                .limit(1)
+            )
+            result = await self._session.execute(stmt)
+            return result.scalar_one_or_none()
         except SQLAlchemyError:
             logger.exception("Profile lookup failed", username=username)
             raise
diff --git a/backend/src/v1/profile/schemas.py b/backend/src/v1/profile/schemas.py
index 64db607..4bb025b 100644
--- a/backend/src/v1/profile/schemas.py
+++ b/backend/src/v1/profile/schemas.py
@@ -1,18 +1,26 @@
 from __future__ import annotations
 
-from pydantic import AnyHttpUrl, BaseModel, Field, field_validator, model_validator
+from pydantic import (
+    AnyHttpUrl,
+    BaseModel,
+    ConfigDict,
+    Field,
+    field_validator,
+    model_validator,
+)
 
 
 class ProfileResponse(BaseModel):
     id: str
     username: str
-    display_name: str | None = None
     avatar_url: str | None = None
     bio: str | None = None
 
 
 class ProfileUpdateRequest(BaseModel):
-    display_name: str | None = Field(default=None, max_length=50)
+    model_config = ConfigDict(extra="forbid")
+
+    username: str | None = Field(default=None, min_length=3, max_length=30)
     avatar_url: str | None = Field(default=None)
     bio: str | None = Field(default=None, max_length=200)
 
@@ -28,6 +36,6 @@ class ProfileUpdateRequest(BaseModel):
 
     @model_validator(mode="after")
     def require_one_field(self) -> "ProfileUpdateRequest":
-        if self.display_name is None and self.avatar_url is None and self.bio is None:
+        if self.username is None and self.avatar_url is None and self.bio is None:
             raise ValueError("At least one field must be provided")
         return self
diff --git a/backend/src/v1/profile/service.py b/backend/src/v1/profile/service.py
index 11449d9..410aa4d 100644
--- a/backend/src/v1/profile/service.py
+++ b/backend/src/v1/profile/service.py
@@ -51,7 +51,6 @@ class ProfileService(BaseService):
         return ProfileResponse(
             id=str(profile.id),
             username=profile.username,
-            display_name=profile.display_name,
             avatar_url=profile.avatar_url,
             bio=profile.bio,
         )
@@ -61,7 +60,7 @@ class ProfileService(BaseService):
         update_data: dict[str, str | None] = {
             key: value
             for key, value in {
-                "display_name": update.display_name,
+                "username": update.username,
                 "avatar_url": update.avatar_url,
                 "bio": update.bio,
             }.items()
@@ -84,7 +83,6 @@ class ProfileService(BaseService):
         return ProfileResponse(
             id=str(profile.id),
             username=profile.username,
-            display_name=profile.display_name,
             avatar_url=profile.avatar_url,
             bio=profile.bio,
         )
@@ -100,7 +98,6 @@ class ProfileService(BaseService):
         return ProfileResponse(
             id=str(profile.id),
             username=profile.username,
-            display_name=profile.display_name,
             avatar_url=profile.avatar_url,
             bio=profile.bio,
         )
diff --git a/backend/tests/e2e/test_auth_flow.py b/backend/tests/e2e/test_auth_flow.py
index 22dac1c..8777d0e 100644
--- a/backend/tests/e2e/test_auth_flow.py
+++ b/backend/tests/e2e/test_auth_flow.py
@@ -95,7 +95,11 @@ def test_auth_flow_e2e() -> None:
                 signup = request_context.post(
                     "/api/v1/auth/signup",
                     data=json.dumps(
-                        {"email": "user@example.com", "password": "secret123"}
+                        {
+                            "username": "demo",
+                            "email": "user@example.com",
+                            "password": "secret123",
+                        }
                     ),
                     headers={"Content-Type": "application/json"},
                 )
diff --git a/backend/tests/e2e/test_profile_flow.py b/backend/tests/e2e/test_profile_flow.py
index da5cb15..b46d2d7 100644
--- a/backend/tests/e2e/test_profile_flow.py
+++ b/backend/tests/e2e/test_profile_flow.py
@@ -27,11 +27,10 @@ class FakeProfileService:
     async def update_me(self, update: ProfileUpdateRequest) -> ProfileResponse:
         return ProfileResponse(
             id=self._profile.id,
-            username=self._profile.username,
-            display_name=(
-                update.display_name
-                if update.display_name is not None
-                else self._profile.display_name
+            username=(
+                update.username
+                if update.username is not None
+                else self._profile.username
             ),
             avatar_url=(
                 update.avatar_url
@@ -75,7 +74,6 @@ def test_profile_flow_e2e() -> None:
     profile = ProfileResponse(
         id=str(user_id),
         username="demo",
-        display_name="Demo User",
         avatar_url=None,
         bio=None,
     )
@@ -98,11 +96,11 @@ def test_profile_flow_e2e() -> None:
 
                 updated = request_context.patch(
                     "/api/v1/profile/me",
-                    data=json.dumps({"display_name": "Updated"}),
+                    data=json.dumps({"username": "updated"}),
                     headers={"Content-Type": "application/json"},
                 )
                 assert updated.status == 200
-                assert updated.json()["display_name"] == "Updated"
+                assert updated.json()["username"] == "updated"
 
                 public = request_context.get("/api/v1/profile/demo")
                 assert public.status == 200
diff --git a/backend/tests/integration/test_auth_routes.py b/backend/tests/integration/test_auth_routes.py
index df25c79..adaaa70 100644
--- a/backend/tests/integration/test_auth_routes.py
+++ b/backend/tests/integration/test_auth_routes.py
@@ -1,14 +1,18 @@
 from __future__ import annotations
 
 from typing import Callable
+from uuid import UUID
 
 from fastapi import HTTPException
 from fastapi.testclient import TestClient
 
 from app import app
+from core.auth.models import CurrentUser
 from v1.auth.dependencies import get_auth_service
+from v1.profile.dependencies import get_current_user
 from v1.auth.schemas import (
     AuthTokenResponse,
+    AuthUserByEmailResponse,
     AuthUser,
     LoginRequest,
     RefreshRequest,
@@ -33,6 +37,16 @@ class FakeAuthService(AuthService):
     async def logout(self, refresh_token: str | None) -> None:
         return None
 
+    async def get_user_by_email(self, email: str) -> AuthUserByEmailResponse:
+        if email == "missing@example.com":
+            raise HTTPException(status_code=404, detail="User not found")
+        return AuthUserByEmailResponse(
+            id="user-1",
+            email=email,
+            created_at="2026-02-24T00:00:00Z",
+            email_confirmed_at=None,
+        )
+
 
 def _override_auth_service(service: AuthService) -> Callable[[], AuthService]:
     def _get_service() -> AuthService:
@@ -58,7 +72,11 @@ def test_signup_returns_token_response() -> None:
     try:
         response = client.post(
             "/api/v1/auth/signup",
-            json={"email": "user@example.com", "password": "secret123"},
+            json={
+                "username": "demo",
+                "email": "user@example.com",
+                "password": "secret123",
+            },
         )
         assert response.status_code == 200
         body = response.json()
@@ -176,3 +194,129 @@ def test_signup_validation_error_returns_problem_details() -> None:
         assert body["detail"] == "Invalid request"
     finally:
         app.dependency_overrides = {}
+
+
+def test_signup_missing_username_returns_problem_details() -> None:
+    user = AuthUser(id="user-1", email="user@example.com")
+    token_response = AuthTokenResponse(
+        access_token="access",
+        refresh_token="refresh",
+        expires_in=3600,
+        token_type="bearer",
+        user=user,
+    )
+    app.dependency_overrides[get_auth_service] = _override_auth_service(
+        FakeAuthService(token_response)
+    )
+
+    client = TestClient(app)
+    try:
+        response = client.post(
+            "/api/v1/auth/signup",
+            json={"email": "user@example.com", "password": "secret123"},
+        )
+        assert response.status_code == 422
+        assert response.headers["content-type"].startswith("application/problem+json")
+        body = response.json()
+        assert body["title"] == "Unprocessable Content"
+        assert body["status"] == 422
+        assert body["detail"] == "Invalid request"
+    finally:
+        app.dependency_overrides = {}
+
+
+def test_get_user_by_email_returns_user() -> None:
+    user = AuthUser(id="user-1", email="user@example.com")
+    token_response = AuthTokenResponse(
+        access_token="access",
+        refresh_token="refresh",
+        expires_in=3600,
+        token_type="bearer",
+        user=user,
+    )
+    app.dependency_overrides[get_auth_service] = _override_auth_service(
+        FakeAuthService(token_response)
+    )
+    app.dependency_overrides[get_current_user] = lambda: CurrentUser(
+        id=UUID("00000000-0000-0000-0000-000000000001"),
+        email="user@example.com",
+    )
+
+    client = TestClient(app)
+    try:
+        response = client.get(
+            "/api/v1/auth/users/by-email",
+            params={"email": "user@example.com"},
+        )
+        assert response.status_code == 200
+        body = response.json()
+        assert body["email"] == "user@example.com"
+        assert body["id"] == "user-1"
+    finally:
+        app.dependency_overrides = {}
+
+
+def test_get_user_by_email_not_found_returns_problem_details() -> None:
+    user = AuthUser(id="user-1", email="user@example.com")
+    token_response = AuthTokenResponse(
+        access_token="access",
+        refresh_token="refresh",
+        expires_in=3600,
+        token_type="bearer",
+        user=user,
+    )
+    app.dependency_overrides[get_auth_service] = _override_auth_service(
+        FakeAuthService(token_response)
+    )
+    app.dependency_overrides[get_current_user] = lambda: CurrentUser(
+        id=UUID("00000000-0000-0000-0000-000000000001"),
+        email="missing@example.com",
+    )
+
+    client = TestClient(app)
+    try:
+        response = client.get(
+            "/api/v1/auth/users/by-email",
+            params={"email": "missing@example.com"},
+        )
+        assert response.status_code == 404
+        assert response.headers["content-type"].startswith("application/problem+json")
+        body = response.json()
+        assert body["title"] == "Not Found"
+        assert body["status"] == 404
+        assert body["detail"] == "User not found"
+    finally:
+        app.dependency_overrides = {}
+
+
+def test_get_user_by_email_forbidden_when_querying_other_user() -> None:
+    user = AuthUser(id="user-1", email="user@example.com")
+    token_response = AuthTokenResponse(
+        access_token="access",
+        refresh_token="refresh",
+        expires_in=3600,
+        token_type="bearer",
+        user=user,
+    )
+    app.dependency_overrides[get_auth_service] = _override_auth_service(
+        FakeAuthService(token_response)
+    )
+    app.dependency_overrides[get_current_user] = lambda: CurrentUser(
+        id=UUID("00000000-0000-0000-0000-000000000001"),
+        email="self@example.com",
+    )
+
+    client = TestClient(app)
+    try:
+        response = client.get(
+            "/api/v1/auth/users/by-email",
+            params={"email": "target@example.com"},
+        )
+        assert response.status_code == 403
+        assert response.headers["content-type"].startswith("application/problem+json")
+        body = response.json()
+        assert body["title"] == "Forbidden"
+        assert body["status"] == 403
+        assert body["detail"] == "Forbidden"
+    finally:
+        app.dependency_overrides = {}
diff --git a/backend/tests/integration/test_profile_routes.py b/backend/tests/integration/test_profile_routes.py
index 07f8165..15a08fa 100644
--- a/backend/tests/integration/test_profile_routes.py
+++ b/backend/tests/integration/test_profile_routes.py
@@ -29,11 +29,10 @@ class FakeProfileService:
             raise HTTPException(status_code=404, detail="Profile not found")
         return ProfileResponse(
             id=self._profile.id,
-            username=self._profile.username,
-            display_name=(
-                update.display_name
-                if update.display_name is not None
-                else self._profile.display_name
+            username=(
+                update.username
+                if update.username is not None
+                else self._profile.username
             ),
             avatar_url=(
                 update.avatar_url
@@ -70,7 +69,6 @@ def test_get_me_returns_profile() -> None:
     profile = ProfileResponse(
         id=str(user_id),
         username="demo",
-        display_name="Demo User",
         avatar_url=None,
         bio=None,
     )
@@ -94,7 +92,6 @@ def test_patch_me_updates_profile() -> None:
     profile = ProfileResponse(
         id=str(user_id),
         username="demo",
-        display_name="Demo User",
         avatar_url=None,
         bio=None,
     )
@@ -107,11 +104,11 @@ def test_patch_me_updates_profile() -> None:
     try:
         response = client.patch(
             "/api/v1/profile/me",
-            json={"display_name": "Updated"},
+            json={"username": "updated"},
         )
         assert response.status_code == 200
         body = response.json()
-        assert body["display_name"] == "Updated"
+        assert body["username"] == "updated"
     finally:
         app.dependency_overrides = {}
 
@@ -120,7 +117,6 @@ def test_get_profile_by_username() -> None:
     profile = ProfileResponse(
         id="00000000-0000-0000-0000-000000000001",
         username="demo",
-        display_name="Demo User",
         avatar_url=None,
         bio=None,
     )
@@ -142,7 +138,6 @@ def test_profile_not_found_returns_problem_details() -> None:
     profile = ProfileResponse(
         id="00000000-0000-0000-0000-000000000001",
         username="demo",
-        display_name="Demo User",
         avatar_url=None,
         bio=None,
     )
@@ -167,7 +162,6 @@ def test_patch_me_validation_error_returns_problem_details() -> None:
     profile = ProfileResponse(
         id=str(user_id),
         username="demo",
-        display_name="Demo User",
         avatar_url=None,
         bio=None,
     )
@@ -186,3 +180,25 @@ def test_patch_me_validation_error_returns_problem_details() -> None:
         assert body["status"] == 422
     finally:
         app.dependency_overrides = {}
+
+
+def test_patch_me_rejects_display_name_field() -> None:
+    user_id = UUID("00000000-0000-0000-0000-000000000001")
+    profile = ProfileResponse(
+        id=str(user_id),
+        username="demo",
+        avatar_url=None,
+        bio=None,
+    )
+    app.dependency_overrides[get_profile_service] = _override_profile_service(
+        FakeProfileService(profile)
+    )
+    app.dependency_overrides[get_current_user] = _override_current_user(user_id)
+
+    client = TestClient(app)
+    try:
+        response = client.patch("/api/v1/profile/me", json={"display_name": "x"})
+        assert response.status_code == 422
+        assert response.headers["content-type"].startswith("application/problem+json")
+    finally:
+        app.dependency_overrides = {}
diff --git a/backend/tests/unit/database/test_base_repository.py b/backend/tests/unit/database/test_base_repository.py
index 0cdb410..9989139 100644
--- a/backend/tests/unit/database/test_base_repository.py
+++ b/backend/tests/unit/database/test_base_repository.py
@@ -4,7 +4,7 @@ from datetime import datetime, timezone
 from uuid import UUID, uuid4
 
 import pytest
-from sqlalchemy import String
+from sqlalchemy import Column, String, Table
 from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
 from sqlalchemy.orm import Mapped, mapped_column
 
@@ -21,10 +21,19 @@ class Widget(SoftDeleteMixin, Base):
 
 @pytest.fixture
 async def db_engine():
+    auth_users = Table(
+        "users",
+        Base.metadata,
+        Column("id", String, primary_key=True),
+        schema="auth",
+        extend_existing=True,
+    )
     engine = create_async_engine("sqlite+aiosqlite:///:memory:", echo=False)
     async with engine.begin() as conn:
+        await conn.exec_driver_sql("ATTACH DATABASE ':memory:' AS auth")
         await conn.run_sync(Base.metadata.create_all)
     yield engine
+    Base.metadata.remove(auth_users)
     await engine.dispose()
 
 
diff --git a/backend/tests/unit/database/test_profile_migration_contract.py b/backend/tests/unit/database/test_profile_migration_contract.py
new file mode 100644
index 0000000..890a339
--- /dev/null
+++ b/backend/tests/unit/database/test_profile_migration_contract.py
@@ -0,0 +1,16 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+
+def test_drop_display_name_migration_exists_and_uses_username_metadata() -> None:
+    versions_dir = Path(__file__).resolve().parents[3] / "alembic" / "versions"
+    migration = (
+        versions_dir / "20260224_drop_profile_display_name_and_trigger_username.py"
+    )
+
+    assert migration.exists()
+
+    content = migration.read_text(encoding="utf-8")
+    assert "DROP COLUMN" in content and "display_name" in content
+    assert "raw_user_meta_data->>'username'" in content
diff --git a/backend/tests/unit/database/test_profile_models.py b/backend/tests/unit/database/test_profile_models.py
index af68cd3..1e9c0b5 100644
--- a/backend/tests/unit/database/test_profile_models.py
+++ b/backend/tests/unit/database/test_profile_models.py
@@ -3,7 +3,7 @@ from __future__ import annotations
 from uuid import uuid4
 
 import pytest
-from sqlalchemy import select
+from sqlalchemy import Column, String, Table, select
 from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
 
 from core.db.base import Base
@@ -13,13 +13,22 @@ from models.profile import Profile
 @pytest.fixture
 async def db_engine():
     """Create in-memory SQLite engine for testing."""
+    users_table = Table(
+        "users",
+        Base.metadata,
+        Column("id", String, primary_key=True),
+        schema="auth",
+        extend_existing=True,
+    )
     engine = create_async_engine(
         "sqlite+aiosqlite:///:memory:",
         echo=False,
     )
     async with engine.begin() as conn:
+        await conn.exec_driver_sql("ATTACH DATABASE ':memory:' AS auth")
         await conn.run_sync(Base.metadata.create_all)
     yield engine
+    Base.metadata.remove(users_table)
     await engine.dispose()
 
 
@@ -43,7 +52,6 @@ async def test_profile_model_create(db_session: AsyncSession) -> None:
     profile = Profile(
         id=profile_id,
         username="testuser",
-        display_name="Test User",
     )
     db_session.add(profile)
     await db_session.commit()
@@ -51,7 +59,6 @@ async def test_profile_model_create(db_session: AsyncSession) -> None:
 
     assert profile.id == profile_id
     assert profile.username == "testuser"
-    assert profile.display_name == "Test User"
     assert profile.created_at is not None
     assert profile.updated_at is not None
     assert profile.deleted_at is None
@@ -64,7 +71,6 @@ async def test_profile_model_get_by_id(db_session: AsyncSession) -> None:
     profile = Profile(
         id=profile_id,
         username="testuser",
-        display_name="Test User",
     )
     db_session.add(profile)
     await db_session.commit()
@@ -80,7 +86,6 @@ async def test_profile_model_get_by_username(db_session: AsyncSession) -> None:
     profile = Profile(
         id=uuid4(),
         username="testuser",
-        display_name="Test User",
     )
     db_session.add(profile)
     await db_session.commit()
@@ -99,16 +104,31 @@ async def test_profile_model_update(db_session: AsyncSession) -> None:
     profile = Profile(
         id=uuid4(),
         username="testuser",
-        display_name="Test User",
         bio="Old bio",
     )
     db_session.add(profile)
     await db_session.commit()
 
-    profile.display_name = "Updated User"
     profile.bio = "New bio"
     await db_session.commit()
     await db_session.refresh(profile)
 
-    assert profile.display_name == "Updated User"
     assert profile.bio == "New bio"
+
+
+@pytest.mark.asyncio
+async def test_profile_model_allows_duplicate_usernames(
+    db_session: AsyncSession,
+) -> None:
+    first = Profile(id=uuid4(), username="same_name")
+    second = Profile(id=uuid4(), username="same_name")
+
+    db_session.add(first)
+    db_session.add(second)
+    await db_session.commit()
+
+    result = await db_session.execute(
+        select(Profile).where(Profile.username == "same_name")
+    )
+    found = result.scalars().all()
+    assert len(found) == 2
diff --git a/backend/tests/unit/v1/auth/test_auth_models.py b/backend/tests/unit/v1/auth/test_auth_models.py
index c4913f3..d94827a 100644
--- a/backend/tests/unit/v1/auth/test_auth_models.py
+++ b/backend/tests/unit/v1/auth/test_auth_models.py
@@ -14,7 +14,14 @@ from v1.auth.schemas import (
 
 def test_signup_requires_valid_email() -> None:
     with pytest.raises(ValidationError):
-        SignupRequest(email="not-an-email", password="secret123")
+        SignupRequest(username="demo", email="not-an-email", password="secret123")
+
+
+def test_signup_requires_username() -> None:
+    with pytest.raises(ValidationError):
+        SignupRequest.model_validate(
+            {"email": "user@example.com", "password": "secret123"}
+        )
 
 
 def test_login_requires_valid_email() -> None:
diff --git a/backend/tests/unit/v1/auth/test_auth_service.py b/backend/tests/unit/v1/auth/test_auth_service.py
index c61a0e1..1981964 100644
--- a/backend/tests/unit/v1/auth/test_auth_service.py
+++ b/backend/tests/unit/v1/auth/test_auth_service.py
@@ -2,8 +2,10 @@ from __future__ import annotations
 
 import pytest
 
+import v1.auth.gateway as auth_gateway_module
 from v1.auth.schemas import (
     AuthTokenResponse,
+    AuthUserByEmailResponse,
     AuthUser,
     LoginRequest,
     RefreshRequest,
@@ -28,6 +30,14 @@ class FakeGateway(AuthServiceGateway):
     async def logout(self, refresh_token: str | None) -> None:
         return None
 
+    async def get_user_by_email(self, email: str) -> AuthUserByEmailResponse:
+        return AuthUserByEmailResponse(
+            id="user-1",
+            email=email,
+            created_at="2026-02-24T00:00:00Z",
+            email_confirmed_at=None,
+        )
+
 
 @pytest.mark.asyncio
 async def test_signup_maps_response() -> None:
@@ -42,7 +52,7 @@ async def test_signup_maps_response() -> None:
     service = AuthService(gateway=FakeGateway(token_response))
 
     result = await service.signup(
-        SignupRequest(email="user@example.com", password="secret123")
+        SignupRequest(username="demo", email="user@example.com", password="secret123")
     )
 
     assert result.access_token == "access"
@@ -66,9 +76,72 @@ class LogoutAssertingGateway(AuthServiceGateway):
     async def logout(self, refresh_token: str | None) -> None:
         assert refresh_token == self._expected_refresh_token
 
+    async def get_user_by_email(self, email: str) -> AuthUserByEmailResponse:
+        raise NotImplementedError
+
 
 @pytest.mark.asyncio
 async def test_logout_forwards_refresh_token() -> None:
     service = AuthService(gateway=LogoutAssertingGateway("refresh-token"))
 
     await service.logout("refresh-token")
+
+
+@pytest.mark.asyncio
+async def test_get_user_by_email_forwards_to_gateway() -> None:
+    user = AuthUser(id="user-1", email="user@example.com")
+    token_response = AuthTokenResponse(
+        access_token="access",
+        refresh_token="refresh",
+        expires_in=3600,
+        token_type="bearer",
+        user=user,
+    )
+    service = AuthService(gateway=FakeGateway(token_response))
+
+    result = await service.get_user_by_email("user@example.com")
+
+    assert result.email == "user@example.com"
+
+
+@pytest.mark.asyncio
+async def test_supabase_signup_passes_username_in_metadata(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    captured_payload: dict[str, object] = {}
+
+    class FakeSupabaseAuth:
+        def sign_up(self, payload: dict[str, object]) -> object:
+            captured_payload.update(payload)
+
+            class _User:
+                id = "user-1"
+                email = "user@example.com"
+
+            class _Session:
+                access_token = "access"
+                refresh_token = "refresh"
+                expires_in = 3600
+                token_type = "bearer"
+
+            class _Response:
+                user = _User()
+                session = _Session()
+
+            return _Response()
+
+    class FakeClient:
+        auth = FakeSupabaseAuth()
+
+    monkeypatch.setattr(auth_gateway_module, "create_client", lambda *_: FakeClient())
+
+    gateway = auth_gateway_module.SupabaseAuthGateway()
+    await gateway.signup(
+        SignupRequest(
+            username="demo",
+            email="user@example.com",
+            password="secret123",
+        )
+    )
+
+    assert captured_payload["data"] == {"username": "demo"}
diff --git a/backend/tests/unit/v1/profile/test_profile_service.py b/backend/tests/unit/v1/profile/test_profile_service.py
index 598e33f..6ed714c 100644
--- a/backend/tests/unit/v1/profile/test_profile_service.py
+++ b/backend/tests/unit/v1/profile/test_profile_service.py
@@ -16,7 +16,6 @@ from v1.profile.service import ProfileService
 def _create_mock_profile(
     user_id: UUID = UUID("00000000-0000-0000-0000-000000000001"),
     username: str = "demo",
-    display_name: str | None = "Demo User",
     avatar_url: str | None = None,
     bio: str | None = None,
 ) -> Profile:
@@ -24,7 +23,6 @@ def _create_mock_profile(
     profile = MagicMock(spec=Profile)
     profile.id = user_id
     profile.username = username
-    profile.display_name = display_name
     profile.avatar_url = avatar_url
     profile.bio = bio
     return profile
@@ -115,9 +113,9 @@ async def test_update_me_updates_fields(mock_session: AsyncMock) -> None:
         current_user=user,
     )
 
-    result = await service.update_me(ProfileUpdateRequest(display_name="Updated"))
+    result = await service.update_me(ProfileUpdateRequest(username="updated"))
 
-    assert result.display_name == "Updated"
+    assert result.username == "updated"
     mock_session.commit.assert_awaited_once()
 
 
@@ -134,7 +132,7 @@ async def test_update_me_no_fields_raises_400(mock_session: AsyncMock) -> None:
 
     # Create a request with all None values by bypassing validation
     update = MagicMock(spec=ProfileUpdateRequest)
-    update.display_name = None
+    update.username = None
     update.avatar_url = None
     update.bio = None
 
diff --git a/backend/tests/unit/v1/profile/test_schemas.py b/backend/tests/unit/v1/profile/test_schemas.py
index f7ee8a8..92ea17c 100644
--- a/backend/tests/unit/v1/profile/test_schemas.py
+++ b/backend/tests/unit/v1/profile/test_schemas.py
@@ -10,7 +10,6 @@ def test_profile_response_maps_fields() -> None:
     response = ProfileResponse(
         id="user-1",
         username="demo",
-        display_name="Demo User",
         avatar_url=None,
         bio=None,
     )
@@ -56,6 +55,11 @@ def test_profile_update_rejects_data_url() -> None:
 
 
 def test_profile_update_accepts_none_avatar_url_with_other_field() -> None:
-    request = ProfileUpdateRequest(display_name="Test", avatar_url=None)
+    request = ProfileUpdateRequest(username="tester", avatar_url=None)
     assert request.avatar_url is None
-    assert request.display_name == "Test"
+    assert request.username == "tester"
+
+
+def test_profile_update_rejects_display_name_field() -> None:
+    with pytest.raises(ValidationError):
+        ProfileUpdateRequest.model_validate({"display_name": "legacy"})
diff --git a/docs/runtime/runtime-runbook.md b/docs/runtime/runtime-runbook.md
index 6ccf92f..7f1bfe9 100644
--- a/docs/runtime/runtime-runbook.md
+++ b/docs/runtime/runtime-runbook.md
@@ -28,18 +28,43 @@ tmux attach -t social-dev
 docker compose --env-file .env -f infra/docker/docker-compose.yml up -d
 
 # 2. 运行迁移和初始化
-docker compose --env-file .env -f infra/docker/docker-compose.yml --profile job run --rm init-job
+docker compose --env-file .env -f infra/docker/docker-compose.yml --profile job run --rm --build init-job
 
 # 3. 一键执行应用层启动（bootstrap + web + workers）
 bash infra/scripts/dev-app-up.sh
 ```
 
+### 生产环境迁移防遗漏（必读）
+
+- 生产发布前必须先通过 bootstrap gate，再启动业务进程；禁止绕过 gate 直接起服务。
+- 使用容器执行迁移时必须带 `--build`，确保最新 Alembic 迁移已进入镜像。
+- 建议在迁移后做一次版本核对，确认已到预期 head。
+
+```bash
+# 1) 先执行 bootstrap gate
+make runtime-bootstrap-gate
+
+# 2) 如采用 init-job 单跑，必须带 --build
+docker compose --env-file .env -f infra/docker/docker-compose.yml --profile job run --rm --build init-job
+
+# 3) 核对 Alembic 版本
+docker compose --env-file .env -f infra/docker/docker-compose.yml exec -T db \
+  psql -U postgres -d postgres -c "SELECT version_num FROM public.alembic_version;"
+```
+
 ### 本地 CLI (开发调试)
 
 > 适用于本地开发调试，不依赖 Docker。
+> 开发调试阶段推荐直接使用本地一次性迁移脚本，不通过 Docker 触发数据库迁移，避免反复重建镜像。
 
 ```bash
-# 初始化/迁移
+# 推荐：一次性迁移（开发调试）
+PYTHONPATH=backend/src uv run python -m core.runtime.cli migrate
+
+# 需要初始化数据时再执行
+PYTHONPATH=backend/src uv run python -m core.runtime.cli init-data
+
+# 或一键执行（migrate + init-data）
 PYTHONPATH=backend/src uv run python -m core.runtime.cli bootstrap
 
 # 启动 Web (gunicorn)
@@ -102,7 +127,7 @@ tmux kill-session -t social-dev
 curl -fsS http://127.0.0.1:${SOCIAL_SUPABASE__KONG_HTTP_PORT:-8000}/health
 
 # 数据库迁移与初始化
-docker compose --env-file .env -f infra/docker/docker-compose.yml --profile job run --rm init-job
+docker compose --env-file .env -f infra/docker/docker-compose.yml --profile job run --rm --build init-job
 ```
 
 ## 查看服务状态
@@ -112,7 +137,30 @@ docker compose --env-file .env -f infra/docker/docker-compose.yml ps
 docker compose --env-file .env -f infra/docker/docker-compose.yml logs -f db
 
 # init-job 为一次性任务（run --rm），如需查看日志请重跑：
-docker compose --env-file .env -f infra/docker/docker-compose.yml --profile job run --rm init-job
+docker compose --env-file .env -f infra/docker/docker-compose.yml --profile job run --rm --build init-job
+```
+
+## Auth/Profile 验证
+
+```bash
+# signup: username + email + password
+curl -sS -X POST http://127.0.0.1:8000/api/v1/auth/signup \
+  -H 'Content-Type: application/json' \
+  -d '{"username":"demo","email":"demo@example.com","password":"secret123"}'
+
+# login: email + password
+curl -sS -X POST http://127.0.0.1:8000/api/v1/auth/login \
+  -H 'Content-Type: application/json' \
+  -d '{"email":"demo@example.com","password":"secret123"}'
+
+# by-email lookup
+curl -sS "http://127.0.0.1:8000/api/v1/auth/users/by-email?email=demo@example.com"
+
+# patch profile: username/avatar_url/bio only
+curl -sS -X PATCH http://127.0.0.1:8000/api/v1/profile/me \
+  -H 'Content-Type: application/json' \
+  -H "Authorization: Bearer <access_token>" \
+  -d '{"username":"demo2","bio":"hello"}'
 ```
 
 ---
@@ -125,3 +173,4 @@ docker compose --env-file .env -f infra/docker/docker-compose.yml --profile job
 | 2026-02-24 | 清理配置：合并 AppSettings 到 WebSettings，删除 Worker 旧配置 (enabled_queues/queues)，统一使用 SOCIAL_WEB__GUNICORN__* 命名 |
 | 2026-02-24 | 开发阶段 compose 暂不编排 web/worker，仅保留 redis/supabase 与 init-job |
 | 2026-02-24 | 新增 dev-app-up 脚本：手动基础设施后，一键 bootstrap + tmux 拉起 web/worker |
+| 2026-02-25 | 补充迁移防遗漏规则：容器迁移命令统一追加 --build；开发调试优先使用本地 CLI 一次性迁移脚本 |