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/database/test_base_repository.py

@@ -0,0 +1,78 @@
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from uuid import UUID, uuid4
+
+import pytest
+from sqlalchemy import String
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+from sqlalchemy.orm import Mapped, mapped_column
+
+from core.db.base import Base, SoftDeleteMixin
+from core.db.base_repository import BaseRepository
+
+
+class Widget(SoftDeleteMixin, Base):
+    __tablename__ = "widgets"
+
+    id: Mapped[UUID] = mapped_column(primary_key=True)
+    name: Mapped[str] = mapped_column(String(50), nullable=False)
+
+
+@pytest.fixture
+async def db_engine():
+    engine = create_async_engine("sqlite+aiosqlite:///:memory:", echo=False)
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+    yield engine
+    await engine.dispose()
+
+
+@pytest.fixture
+async def db_session(db_engine):
+    async_session = async_sessionmaker(
+        bind=db_engine,
+        class_=AsyncSession,
+        expire_on_commit=False,
+    )
+    async with async_session() as session:
+        yield session
+        await session.rollback()
+
+
+@pytest.mark.asyncio
+async def test_get_by_id_filters_soft_deleted(db_session: AsyncSession) -> None:
+    repository = BaseRepository(db_session, Widget)
+    widget_id = uuid4()
+
+    widget = Widget(id=widget_id, name="widget")
+    db_session.add(widget)
+    await db_session.commit()
+
+    found = await repository.get_by_id(widget_id)
+    assert found is not None
+
+    deleted = await repository.soft_delete_by_id(widget_id)
+    assert deleted is not None
+    assert deleted.deleted_at is not None
+
+    missing = await repository.get_by_id(widget_id)
+    assert missing is None
+
+
+@pytest.mark.asyncio
+async def test_soft_delete_sets_timestamp(db_session: AsyncSession) -> None:
+    repository = BaseRepository(db_session, Widget)
+    widget_id = uuid4()
+
+    widget = Widget(id=widget_id, name="widget")
+    db_session.add(widget)
+    await db_session.commit()
+
+    deleted = await repository.soft_delete_by_id(widget_id)
+    assert deleted is not None
+    assert isinstance(deleted.deleted_at, datetime)
+    deleted_at = deleted.deleted_at
+    if deleted_at.tzinfo is None:
+        deleted_at = deleted_at.replace(tzinfo=timezone.utc)
+    assert deleted_at <= datetime.now(timezone.utc)