Bulletproof the update auto-refresh with fallback mechanisms (related to #671)

After the initial fix, added multiple layers of reliability to ensure updates
ALWAYS auto-refresh, even in edge cases:

1. Fallback polling: GlobalUpdateProgressWatcher now polls /api/updates/status
   every 5 seconds as a safety net in case WebSocket events are dropped, missed,
   or the tab connects mid-update. This ensures tabs that join late or have
   WebSocket issues still detect in-progress updates.

2. Manual reload button: Added "Reload Now" button in UpdateProgressModal that
   appears after 5+ health check attempts during restart. Gives users an escape
   hatch if auto-reload is delayed (slow DNS, reverse proxy issues, etc.).

3. Already protected: Modal close button only shows when update is complete,
   preventing users from accidentally closing it mid-update.

These changes address all failure modes identified:
- Tabs without WebSocket: covered by polling fallback
- Tabs joining mid-update: covered by polling fallback
- Health check delays: covered by manual reload button
- User accidentally closing modal: already prevented

The combination of WebSocket events (primary), polling (fallback), health checks
(restart detection), and manual reload (escape hatch) should make this bulletproof.

frontend-modern/src/App.tsx

@@ -121,8 +121,30 @@ function GlobalUpdateProgressWatcher() {
   const navigate = useNavigate();
   const [showProgressModal, setShowProgressModal] = createSignal(false);
   const [hasAutoOpened, setHasAutoOpened] = createSignal(false);
+  let pollInterval: number | undefined;
 
-  // Watch for update progress events from WebSocket
+  // Fallback polling in case WebSocket events are missed
+  const pollUpdateStatus = async () => {
+    try {
+      const status = await UpdatesAPI.getUpdateStatus();
+      const inProgress = isUpdateInProgress(status.status);
+
+      if (inProgress && !showProgressModal() && !hasAutoOpened()) {
+        logger.info('Update in progress detected via polling fallback, showing progress modal', {
+          status: status.status,
+          message: status.message,
+        });
+        setShowProgressModal(true);
+        setHasAutoOpened(true);
+      } else if (!inProgress && hasAutoOpened()) {
+        setHasAutoOpened(false);
+      }
+    } catch (error) {
+      // Silently ignore polling errors
+    }
+  };
+
+  // Watch for update progress events from WebSocket (primary mechanism)
   createEffect(() => {
     const progress = wsContext?.updateProgress?.() as UpdateStatus | null;
 
@@ -148,6 +170,18 @@ function GlobalUpdateProgressWatcher() {
     }
   });
 
+  // Start fallback polling on mount, stop on cleanup
+  onMount(() => {
+    // Poll every 5 seconds as a safety net
+    pollInterval = setInterval(pollUpdateStatus, 5000) as unknown as number;
+  });
+
+  onCleanup(() => {
+    if (pollInterval) {
+      clearInterval(pollInterval);
+    }
+  });
+
   return (
     <UpdateProgressModal
       isOpen={showProgressModal()}

frontend-modern/src/components/UpdateProgressModal.tsx

@@ -307,11 +307,21 @@ export function UpdateProgressModal(props: UpdateProgressModalProps) {
                     <svg class="w-5 h-5 text-blue-600 dark:text-blue-400 flex-shrink-0 mt-0.5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                       <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M13 16h-1v-4h-1m1-4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z" />
                     </svg>
-                    <div class="text-sm text-blue-800 dark:text-blue-200">
-                      <Show when={wsDisconnected()} fallback={
-                        <span>Pulse is restarting with the new version...</span>
-                      }>
-                        <span>Waiting for Pulse to complete restart. This page will reload automatically.</span>
+                    <div class="flex-1">
+                      <div class="text-sm text-blue-800 dark:text-blue-200">
+                        <Show when={wsDisconnected()} fallback={
+                          <span>Pulse is restarting with the new version...</span>
+                        }>
+                          <span>Waiting for Pulse to complete restart. This page will reload automatically.</span>
+                        </Show>
+                      </div>
+                      <Show when={wsDisconnected() && healthCheckAttempts > 5}>
+                        <button
+                          onClick={() => window.location.reload()}
+                          class="mt-2 px-3 py-1.5 text-xs font-medium text-white bg-blue-600 hover:bg-blue-700 rounded transition-colors"
+                        >
+                          Reload Now
+                        </button>
                       </Show>
                     </div>
                   </div>