Add web push

frontend/public/sw.js

@@ -1,12 +1,59 @@
-// Minimal service worker required for PWA installability.
-// No caching — this app is network-dependent. All fetches pass through.
+/* Service worker for PWA installability and Web Push notifications. */
 
-self.addEventListener("install", function () {
+self.addEventListener("install", () => {
   self.skipWaiting();
 });
 
-self.addEventListener("activate", function (event) {
+self.addEventListener("activate", (event) => {
   event.waitUntil(self.clients.claim());
 });
 
-self.addEventListener("fetch", function () {});
+// No-op fetch handler — required for PWA installability criteria.
+// We don't cache anything; the app always fetches from the network.
+self.addEventListener("fetch", () => {});
+
+self.addEventListener("push", (event) => {
+  let data = {};
+  try {
+    data = event.data ? event.data.json() : {};
+  } catch {
+    data = { title: "New message", body: event.data?.text() || "" };
+  }
+
+  const title = data.title || "New message";
+  const options = {
+    body: data.body || "",
+    icon: "./favicon-256x256.png",
+    badge: "./favicon-96x96.png",
+    tag: data.tag || "meshcore-push",
+    data: { url_hash: data.url_hash || "" },
+  };
+
+  event.waitUntil(self.registration.showNotification(title, options));
+});
+
+self.addEventListener("notificationclick", (event) => {
+  event.notification.close();
+  const urlHash = event.notification.data?.url_hash || "";
+
+  event.waitUntil(
+    clients
+      .matchAll({ type: "window", includeUncontrolled: true })
+      .then((windowClients) => {
+        // Focus an existing tab if one is open
+        for (const client of windowClients) {
+          if (client.url.includes(self.location.origin)) {
+            client.focus();
+            if (urlHash) {
+              client.navigate(self.location.origin + "/" + urlHash);
+            }
+            return;
+          }
+        }
+        // Otherwise open a new tab
+        return clients.openWindow(
+          self.location.origin + "/" + (urlHash || "")
+        );
+      })
+  );
+});