fix: The url output by the list_operator is null

The url can be output in the first or last data obtained by list_operator. After reference, url is not a field of File model, but a field processed by self.generate_url(). However, the code uses the direct output of remote_url, which is often an incomplete field or null, so it is more reasonable to replace it with a field generated by generate_url()

api/core/workflow/nodes/list_operator/node.py

@@ -176,7 +176,7 @@ def _get_file_extract_string_func(*, key: str) -> Callable[[File], str]:
         case "transfer_method":
             return lambda x: x.transfer_method
         case "url":
-            return lambda x: x.remote_url or ""
+            return lambda x: x.generate_url() or ""
         case _:
             raise InvalidKeyError(f"Invalid key: {key}")