refactor(db): 修复异步连接池无界增长，并完成 SQLAlchemy 2.0 迁移与分层归位 (#6320)

app/db/models/systemconfig.py

@@ -1,6 +1,7 @@
-from sqlalchemy import Column, String, JSON, select
+from typing import Any, Optional
+from sqlalchemy import String, JSON, select
 from sqlalchemy.ext.asyncio import AsyncSession
-from sqlalchemy.orm import Session
+from sqlalchemy.orm import Mapped, Session, mapped_column
 
 from app.db import db_query, db_update, Base, async_db_query, get_id_column
 
@@ -11,14 +12,14 @@ class SystemConfig(Base):
     """
     id = get_id_column()
     # 主键
-    key = Column(String, index=True)
+    key: Mapped[Optional[str]] = mapped_column(String, index=True)
     # 值
-    value = Column(JSON)
+    value: Mapped[Optional[Any]] = mapped_column(JSON)
 
     @classmethod
     @db_query
     def get_by_key(cls, db: Session, key: str):
-        return db.query(cls).filter(cls.key == key).first()
+        return db.execute(select(cls).where(cls.key == key)).scalars().first()
 
     @classmethod
     @async_db_query