Add initial project files

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/database.py

@@ -0,0 +1,20 @@
+from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker, AsyncSession
+from sqlalchemy.orm import DeclarativeBase
+
+from app.config import settings
+
+
+engine = create_async_engine(settings.database_url, echo=False)
+AsyncSessionLocal = async_sessionmaker(engine, expire_on_commit=False)
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+async def init_db() -> None:
+    # Import models so their tables are registered on Base.metadata before create_all
+    from app.models import user, entry  # noqa: F401
+
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)