Use the new "form-fetch-action" for better user experience, and use
JSONError to show error messages.
---------
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Fixes: https://github.com/go-gitea/gitea/issues/36152
Enable the `nilnil` linter while adding `//nolint` comments to existing
violations. This will ensure no new issues enter the code base while we
can fix existing issues gradually.
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
