feat: 添加 SQLAlchemy 模型 + Alembic 数据库迁移

app/main.py

@@ -1,7 +1,17 @@
 import logging
 from contextlib import asynccontextmanager
 from fastapi import FastAPI
+from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker, AsyncSession
 from app.config import settings
+from app.models.announcement import Base
+
+engine = create_async_engine(settings.database_url, echo=settings.debug)
+async_session = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
+
+
+async def get_db() -> AsyncSession:
+    async with async_session() as session:
+        yield session
 
 
 @asynccontextmanager
@@ -11,6 +21,7 @@ async def lifespan(app: FastAPI):
         format="%(asctime)s [%(levelname)s] %(name)s: %(message)s",
     )
     yield
+    await engine.dispose()
 
 
 app = FastAPI(