fix(sync): 优先级同步前置过滤远端失效账号防排序污染，移除 locals 隐患，并将自愈结果纳入本地日志与摘要统计

backend/app/services/website_client.py

@@ -225,7 +225,12 @@ class Sub2ApiWebsiteClient:
 
     def update_account(self, account_id: str, body: dict[str, Any], endpoint: str = "/accounts") -> dict[str, Any]:
         """更新远端账号（仅传入需要变更的字段）。"""
-        resp = self._request("PUT", f"{endpoint}/{account_id}", body)
+        try:
+            resp = self._request("PUT", f"{endpoint}/{account_id}", body)
+        except WebsiteError as exc:
+            if isinstance(exc.__cause__, httpx.HTTPStatusError) and exc.__cause__.response.status_code == 404:
+                raise WebsiteError(f"目标账号 {account_id} 不存在或已被删除") from exc.__cause__
+            raise
         data = _unwrap_data(resp)
         return data if isinstance(data, dict) else {"value": data}