Show raw HTTP status and response in sync error callback for diagnosis

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

upload/admin/view/template/extension/module/reverb.twig

@@ -251,8 +251,13 @@ $(function() {
                     $result.removeClass('text-success').addClass('text-danger').text(data.error).show();
                 }
             },
-            error: function() {
-                $result.removeClass('text-success').addClass('text-danger').text('Sync request failed.').show();
+            error: function(xhr) {
+                var info = 'HTTP ' + xhr.status;
+                if (xhr.responseText) {
+                    var preview = xhr.responseText.replace(/<[^>]+>/g, ' ').replace(/\s+/g, ' ').trim().substring(0, 300);
+                    if (preview) info += ': ' + preview;
+                }
+                $result.removeClass('text-success').addClass('text-danger').text(info).show();
             },
             complete: function() {
                 $btn.prop('disabled', false).html('<i class="fa fa-refresh"></i> {{ button_sync_now }}');