Initial Claude implementation

app/core/database.py

@@ -0,0 +1,46 @@
+"""Async SQLAlchemy engine, session factory, and declarative base.
+
+Works with SQLite (aiosqlite) or Postgres (asyncpg) depending on DATABASE_URL.
+"""
+from collections.abc import AsyncGenerator
+
+from sqlalchemy.ext.asyncio import (
+    AsyncSession,
+    async_sessionmaker,
+    create_async_engine,
+)
+from sqlalchemy.orm import DeclarativeBase
+
+from app.core.config import settings
+
+
+class Base(DeclarativeBase):
+    """Declarative base shared by all models."""
+
+
+engine = create_async_engine(settings.database_url, echo=settings.debug, future=True)
+
+AsyncSessionLocal = async_sessionmaker(
+    engine,
+    class_=AsyncSession,
+    expire_on_commit=False,
+    autoflush=False,
+)
+
+
+async def get_db() -> AsyncGenerator[AsyncSession, None]:
+    """FastAPI dependency yielding a request-scoped session."""
+    async with AsyncSessionLocal() as session:
+        yield session
+
+
+async def init_db() -> None:
+    """Create all tables. Convenient for dev/SQLite and tests.
+
+    In production prefer Alembic migrations (``alembic upgrade head``).
+    """
+    # Import models so they register with Base.metadata before create_all.
+    import app.models  # noqa: F401
+
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)