feat: add loading spinner during credentials fetch

.claude/JOURNAL.md

@@ -87,3 +87,9 @@ This journal tracks substantive work on documents, diagrams, and documentation c
 
 28. **Task - Fix admin template URL handling**: Fixed fetch interceptor and nav links in templates_enhanced<br>
     **Result**: Fixed `isUserCreation` check in admin.html to strip query params (`?_xsrf=...`) before checking if URL ends with `api/users` - React admin adds XSRF token as query param which broke the endpoint detection. Fixed double "hub" prefix in page.html nav links - changed `{{ base_url }}hub/authorize` to `{{ base_url }}authorize` and `{{ base_url }}hub/change-password` to `{{ base_url }}change-password` since base_url already includes `/hub/`
+
+29. **Task - Fix credentials API route conflict**: Changed credentials endpoint from `/api/users/credentials` to `/api/admin/credentials`<br>
+    **Result**: JupyterHub's built-in `/api/users/*` handler was catching requests before custom handler, returning "Invalid JSON keys" error. Changed route in jupyterhub_config.py, admin.html, and custom_handlers.py docstring
+
+30. **Task - Credentials modal UX improvements**: Enhanced modal layout, scrolling, and loading feedback<br>
+    **Result**: Moved Copy/Download buttons to top of modal body. Added scrollable container (max-height 300px) for long user lists. Removed `<code>` styling for plain text display. Added loading spinner modal shown between user creation and credentials display. Improved Makefile version output format to show "Current version" and "New version" lines

services/jupyterhub/templates_enhanced/admin.html

@@ -51,6 +51,20 @@
       </div>
     </div>
   </div>
+
+  <!-- Loading Spinner Modal -->
+  <div class="modal fade" id="loading-modal" tabindex="-1" role="dialog" data-bs-backdrop="static" data-bs-keyboard="false" aria-hidden="true">
+    <div class="modal-dialog modal-sm modal-dialog-centered" role="document">
+      <div class="modal-content">
+        <div class="modal-body text-center py-4">
+          <div class="spinner-border text-primary mb-3" role="status">
+            <span class="visually-hidden">Loading...</span>
+          </div>
+          <div>Generating credentials...</div>
+        </div>
+      </div>
+    </div>
+  </div>
 {% endblock main %}
 
 {% block footer %}
@@ -131,6 +145,9 @@
                         console.log('[Admin] Users created:', createdUsers);
                         pendingUsernames.push(...createdUsers);
 
+                        // Show loading spinner
+                        showLoadingSpinner();
+
                         // Debounce - wait for batch completion then fetch credentials
                         clearTimeout(window._credentialsFetchTimeout);
                         window._credentialsFetchTimeout = setTimeout(() => {
@@ -172,14 +189,32 @@
                 }
             } else {
                 console.error('[Admin] Failed to fetch credentials:', response.status);
+                hideLoadingSpinner();
             }
         } catch (e) {
             console.error('[Admin] Error fetching credentials:', e);
+            hideLoadingSpinner();
+        }
+    }
+
+    // Loading spinner functions
+    let loadingModal = null;
+    function showLoadingSpinner() {
+        const modalEl = document.getElementById('loading-modal');
+        if (!loadingModal) {
+            loadingModal = new bootstrap.Modal(modalEl);
+        }
+        loadingModal.show();
+    }
+    function hideLoadingSpinner() {
+        if (loadingModal) {
+            loadingModal.hide();
         }
     }
 
     // Show modal with credentials
     function showCredentialsModal(credentials) {
+        hideLoadingSpinner();
         const tbody = document.getElementById('credentials-body');
         tbody.innerHTML = '';