fix: 对齐 test_account 在 404 响应下的日志成功标志及错误类型口径，与标准接口行为一致

backend/app/services/website_client.py

@@ -380,6 +380,8 @@ class Sub2ApiWebsiteClient:
                 with self._client.stream("POST", url, headers=headers) as response:
                     status_code = response.status_code
                     if response.status_code == 404:
+                        error_type = "HTTPStatus"
+                        error_msg = "HTTP 404"
                         return {"status": "404", "cleanup_allowed": True, "message": "账号在远端不存在 (404)"}
                     if response.status_code >= 400:
                         response.raise_for_status()

backend/test_cleanup_invalid_accounts.py

@@ -95,7 +95,9 @@ def test_website_client_test_account_sse_scenarios(monkeypatch):
     assert res["cleanup_allowed"] is True
     assert len(log_calls) == 3
     assert log_calls[-1]["status_code"] == 404
-    assert log_calls[-1]["success"] is True
+    assert log_calls[-1]["success"] is False
+    assert log_calls[-1]["error_type"] == "HTTPStatus"
+    assert log_calls[-1]["error_message"] == "HTTP 404"
 
     # 4. error event
     monkeypatch.setattr(c._client, "stream", mock_stream(200, ["event: error", "data: \"internal error\""]))