Refactor code structure for improved readability and maintainability

frontend/vue-app/public/sw.js

@@ -1,5 +1,14 @@
 /* Service Worker for Reward App push notifications */
 
+/* Activate immediately — no waiting for old tabs to close */
+self.addEventListener('install', function (event) {
+  event.waitUntil(self.skipWaiting())
+})
+
+self.addEventListener('activate', function (event) {
+  event.waitUntil(self.clients.claim())
+})
+
 self.addEventListener('push', function (event) {
   if (!event.data) return
 
@@ -13,6 +22,7 @@ self.addEventListener('push', function (event) {
   const title = payload.title || 'Reward App'
   const options = {
     body: payload.body || '',
+    icon: '/icons/icon-192x192.png',
     data: payload,
     actions: [
       { action: 'approve', title: 'Approve' },