fix(douyu): reject invalid activity cookies

web/backend/services/douyu_service.py

@@ -145,9 +145,9 @@ def ensure_douyu_config(db: Session) -> DouyuConfig:
     return config
 
 
-def latest_success_cookie(db: Session, account_id: int) -> str:
-    """读取账号最近一次成功登录 Cookie。"""
-    task = (
+def latest_success_login_task(db: Session, account_id: int) -> LoginTask | None:
+    """读取账号最近一次成功登录记录。"""
+    return (
         db.query(LoginTask)
         .filter(
             LoginTask.account_id == account_id,
@@ -157,6 +157,11 @@ def latest_success_cookie(db: Session, account_id: int) -> str:
         .order_by(LoginTask.id.desc())
         .first()
     )
+
+
+def latest_success_cookie(db: Session, account_id: int) -> str:
+    """读取账号最近一次成功登录 Cookie。"""
+    task = latest_success_login_task(db, account_id)
     return task.cookie if task else ""