feat: integrate Firebase Cloud Messaging for push notifications

public/firebase-messaging-sw.js

@@ -0,0 +1,38 @@
+// Firebase Cloud Messaging Service Worker
+// This file MUST be in the public/ directory (served at /firebase-messaging-sw.js)
+
+importScripts("https://www.gstatic.com/firebasejs/10.12.0/firebase-app-compat.js");
+importScripts("https://www.gstatic.com/firebasejs/10.12.0/firebase-messaging-compat.js");
+
+firebase.initializeApp({
+  apiKey: "AIzaSyBZV7KBLRJSTApahfrO8lBesmIM3zNRSaY",
+  authDomain: "sweet-home-b2766.firebaseapp.com",
+  projectId: "sweet-home-b2766",
+  storageBucket: "sweet-home-b2766.firebasestorage.app",
+  messagingSenderId: "602865114600",
+  appId: "1:602865114600:web:ed9b6754940507a6ab585d",
+  measurementId: "G-M2V95NBJLX",
+});
+
+const messaging = firebase.messaging();
+
+// Handle background messages
+messaging.onBackgroundMessage((payload) => {
+  console.log("[FCM SW] Background message:", payload);
+  const title = payload.notification?.title || payload.data?.title || "Sweet Home";
+  const options = {
+    body: payload.notification?.body || payload.data?.body || "",
+    icon: payload.notification?.icon || "/logo.png",
+    badge: "/logo.png",
+    data: payload.data,
+    tag: "sweethome-notification",
+  };
+  self.registration.showNotification(title, options);
+});
+
+// Handle notification click
+self.addEventListener("notificationclick", (event) => {
+  event.notification.close();
+  const url = event.notification.data?.url || "/";
+  event.waitUntil(clients.openWindow(url));
+});