Add service worker for push notifications

public/sw.js

@@ -0,0 +1,41 @@
+/* eslint-disable no-restricted-globals */
+
+self.addEventListener('push', (event) => {
+  if (!event.data) return;
+
+  try {
+    const payload = event.data.json();
+    const options = {
+      body: payload.body,
+      icon: payload.icon || '/favicon.ico',
+      badge: '/favicon.ico',
+      data: { url: payload.url || '/' },
+    };
+
+    event.waitUntil(self.registration.showNotification(payload.title, options));
+  } catch {
+    // Silently fail
+  }
+});
+
+self.addEventListener('notificationclick', (event) => {
+  event.notification.close();
+
+  const url = event.notification.data?.url || '/';
+
+  event.waitUntil(
+    self.clients
+      .matchAll({ type: 'window', includeUncontrolled: true })
+      .then((clientList) => {
+        // Focus existing window if available
+        for (const client of clientList) {
+          if (client.url.includes(self.location.origin)) {
+            client.navigate(url);
+            return client.focus();
+          }
+        }
+        // Otherwise open new window
+        return self.clients.openWindow(url);
+      }),
+  );
+});