PWA installability + working service worker (wishlist #8)

manifest.webmanifest with the existing icons, apple-touch-icon, and SW
registration at startup. The old sw.js was a self-unregistering cleanup
stub — meaning serviceWorker.ready never resolved and web push has been
silently dead; the new worker handles push display and notification
clicks, and makes the app installable.

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

frontend/public/sw.js

@@ -1,4 +1,42 @@
+/* WealthySmart service worker: web push + PWA installability.
+ * (Replaces the old self-unregistering cleanup stub, which also meant
+ * `navigator.serviceWorker.ready` never resolved and push silently no-oped.) */
+
 self.addEventListener("install", () => self.skipWaiting());
-self.addEventListener("activate", async () => {
-  await self.registration.unregister();
+
+self.addEventListener("activate", (event) => {
+  event.waitUntil(self.clients.claim());
+});
+
+self.addEventListener("push", (event) => {
+  let data = { title: "WealthySmart", body: "", url: "/" };
+  try {
+    data = { ...data, ...event.data.json() };
+  } catch {
+    if (event.data) data.body = event.data.text();
+  }
+  event.waitUntil(
+    self.registration.showNotification(data.title, {
+      body: data.body,
+      icon: "/icons/icon-192.png",
+      badge: "/icons/icon-192.png",
+      data: { url: data.url },
+    }),
+  );
+});
+
+self.addEventListener("notificationclick", (event) => {
+  event.notification.close();
+  const url = event.notification.data?.url || "/";
+  event.waitUntil(
+    self.clients.matchAll({ type: "window", includeUncontrolled: true }).then((clients) => {
+      for (const client of clients) {
+        if ("focus" in client) {
+          client.navigate(url);
+          return client.focus();
+        }
+      }
+      return self.clients.openWindow(url);
+    }),
+  );
 });