fix(routers+imports): fix missing DetectionRule import and correct -> list return type annotations that actually return paginated dicts

backend/app/routers/campaigns.py

@@ -190,7 +190,7 @@ def list_campaigns(
     db: Session = Depends(get_db),
     # Entry: current_user
     current_user: User = Depends(get_current_user),
-) -> list:
+) -> dict:
     """List campaigns with optional filters and pagination.
 
     Args: