fix: API 全部改用显式两步走 await session.execute + result.scalars()

之前 (await ...).scalars() 链式在 SQLAlchemy 2.0 async 下报
'coroutine' has no attribute 'scalars' 错误。改为先 await 拿 result
再 .scalars(),这是 SQLAlchemy 2.0 推荐的 async 写法。

backend/app/api/admin.py

@@ -29,7 +29,9 @@ router = APIRouter(prefix="/admin", tags=["admin"], dependencies=[Depends(requir
 # === Source CRUD ===
 @router.get("/sources", response_model=list[SourceOut])
 async def list_sources_all(session: AsyncSession = Depends(get_session)):
-    rows = (await session.execute(select(Source).order_by(Source.id))).scalars()
+    result = await session.execute(select(Source).order_by(Source.id))
+
+    rows = result.scalars()
     return [SourceOut.model_validate(s) for s in rows]
 
 
@@ -65,7 +67,7 @@ async def update_source(
     body: SourceUpdate,
     session: AsyncSession = Depends(get_session),
 ):
-    src = (await session.execute(select(Source).where(Source.id == source_id))).scalar_one_or_none()
+    result = await session.execute(select(Source).where(Source.id == source_id))).scalar_one_or_none()
     if not src:
         raise HTTPException(status.HTTP_404_NOT_FOUND, "Source not found")
     for k, v in body.model_dump(exclude_unset=True).items():
@@ -155,7 +157,8 @@ class HealthOut(BaseModel):
 
 @router.get("/health", response_model=list[HealthOut])
 async def health(session: AsyncSession = Depends(get_session)):
-    rows = (await session.execute(select(Source).order_by(Source.priority.desc()))).scalars()
+    result = await session.execute(select(Source).order_by(Source.priority.desc()))
+    rows = result.scalars()
     out: list[HealthOut] = []
     for s in rows:
         c24 = (