refactor: align backend layout and supabase infra

Consolidate backend modules/tests under the backend package while syncing Supabase compose/env config and related plans.

backend/tests/unit/v1/auth/test_auth_models.py

@@ -0,0 +1,41 @@
+from __future__ import annotations
+
+import pytest
+from pydantic import ValidationError
+
+from v1.auth.models import (
+    AuthTokenResponse,
+    AuthUser,
+    LoginRequest,
+    RefreshRequest,
+    SignupRequest,
+)
+
+
+def test_signup_requires_valid_email() -> None:
+    with pytest.raises(ValidationError):
+        SignupRequest(email="not-an-email", password="secret123")
+
+
+def test_login_requires_valid_email() -> None:
+    with pytest.raises(ValidationError):
+        LoginRequest(email="invalid", password="secret123")
+
+
+def test_refresh_requires_token() -> None:
+    with pytest.raises(ValidationError):
+        RefreshRequest(refresh_token="")
+
+
+def test_auth_token_response_maps_user() -> None:
+    user = AuthUser(id="user-1", email="user@example.com")
+    response = AuthTokenResponse(
+        access_token="access",
+        refresh_token="refresh",
+        expires_in=3600,
+        token_type="bearer",
+        user=user,
+    )
+
+    assert response.user.id == "user-1"
+    assert response.user.email == "user@example.com"