feat: PWA manifest, app icons, service worker with tests

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

public/app.js

@@ -216,6 +216,19 @@ async function requestWakeLock() {
   }
 }
 
+/* ---------- service worker ---------- */
+
+function registerServiceWorker() {
+  if (!('serviceWorker' in navigator)) return;
+  navigator.serviceWorker.register('./sw.js').catch((err) => console.warn('weerscherm: service worker', err));
+  let reloading = false;
+  navigator.serviceWorker.addEventListener('controllerchange', () => {
+    if (reloading) return;
+    reloading = true;
+    location.reload();
+  });
+}
+
 /* ---------- start ---------- */
 
 window.addEventListener('resize', fit);
@@ -225,6 +238,7 @@ document.addEventListener('visibilitychange', () => {
     fit();
     refresh();
     requestWakeLock();
+registerServiceWorker();
   }
 });
 
@@ -236,3 +250,4 @@ scheduleClock();
 scheduleMidnight();
 scheduleReload();
 requestWakeLock();
+registerServiceWorker();