feat: add settings and async db engine

backend/app/db.py

@@ -0,0 +1,16 @@
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+from sqlalchemy.orm import DeclarativeBase
+
+from app.config import settings
+
+engine = create_async_engine(settings.database_url, echo=False)
+async_session_maker = async_sessionmaker(engine, expire_on_commit=False)
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+async def get_db() -> AsyncSession:
+    async with async_session_maker() as session:
+        yield session