Refresh the page automatically after a pending offline sync completes

The real dashboard is server-rendered before any client JS runs, so
the first page load after reconnecting always reflects the pre-sync
database state -- the background sync then completes silently, but
nothing told that already-rendered page to update. A task created
offline would appear to vanish until the next navigation happened to
load fresh data. runBackgroundSync() now reports whether it pushed
pending changes, and both places that trigger it automatically reload
the page when it did.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

static/js/app.js

@@ -11,8 +11,11 @@ document.addEventListener('DOMContentLoaded', function() {
     maybeBackgroundSync();
 });
 
-window.addEventListener('online', function() {
-    runBackgroundSync();
+window.addEventListener('online', async function() {
+    const pushedChanges = await runBackgroundSync();
+    if (pushedChanges) {
+        window.location.reload();
+    }
 });
 
 /* ============================================