fix onboarding bugs

app/assets/js/custom.js

@@ -820,6 +820,13 @@ function ajax_request(options) {
       throw xhr;
     }
 
+    // File / payload too large (nginx 413)
+    if (xhr?.status === 413) {
+      bootbox.alert('The file you selected is too large. Please use an image under 2 MB and try again.');
+      options.onError?.(xhr, 'payload_too_large');
+      throw xhr;
+    }
+
     // Usage limit reached — show upgrade notice instead of generic error
     if (xhr?.status === 402) {
       const d = xhr?.responseJSON ?? {};