重构数据库连接管理，添加元数据支持

app/infra/db/metadata/database.py

@@ -0,0 +1,27 @@
+import logging
+from typing import AsyncGenerator
+
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+
+from app.core.config import settings
+
+logger = logging.getLogger(__name__)
+
+engine = create_async_engine(
+    settings.METADATA_DATABASE_URI,
+    pool_size=settings.METADATA_DB_POOL_SIZE,
+    max_overflow=settings.METADATA_DB_MAX_OVERFLOW,
+    pool_pre_ping=True,
+)
+
+SessionLocal = async_sessionmaker(engine, expire_on_commit=False)
+
+
+async def get_metadata_session() -> AsyncGenerator[AsyncSession, None]:
+    async with SessionLocal() as session:
+        yield session
+
+
+async def close_metadata_engine() -> None:
+    await engine.dispose()
+    logger.info("Metadata database engine disposed.")