Sync offline cache on every page load, not just every 2 minutes

Online-side mutations (e.g. deleting a tag) only update the server, not
IndexedDB, so a throttled background sync could leave the offline cache
stale for up to two minutes. Going offline in that window resurrected
deleted/stale data (e.g. a deleted tag reappearing). Removing the throttle
so every real page load pulls fresh state keeps the offline cache in
sync with whatever was just done online.

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

static/js/app.js

@@ -3,12 +3,20 @@
  * Handles theme toggle, task selection, mobile menus, and AJAX operations
  */
 
-document.addEventListener('DOMContentLoaded', function() {
+document.addEventListener('DOMContentLoaded', async function() {
     initTheme();
     initTaskSelection();
     initTimerDisplays();
     registerServiceWorker();
-    maybeBackgroundSync();
+    // Every real page load is a chance for the online UI to have mutated
+    // something (a tag delete, a task edit) that IndexedDB doesn't know
+    // about yet - sync unconditionally (no throttle) so the offline cache
+    // never lags behind what the user just did while online. The server's
+    // own rate limit (SyncRateThrottle) is the backstop against excess calls.
+    const pushedChanges = await runBackgroundSync();
+    if (pushedChanges) {
+        window.location.reload();
+    }
 });
 
 window.addEventListener('online', async function() {