首个可运行的版本

backend/app/database.py

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+"""异步数据库引擎和会话管理"""
+
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+from sqlalchemy.orm import DeclarativeBase
+
+from app.config import settings
+
+# 异步引擎
+engine = create_async_engine(
+    settings.DATABASE_URL,
+    echo=False,
+    pool_size=20,
+    max_overflow=10,
+)
+
+# 异步会话工厂
+async_session = async_sessionmaker(
+    engine,
+    class_=AsyncSession,
+    expire_on_commit=False,
+)
+
+
+# 声明式基类
+class Base(DeclarativeBase):
+    pass