feat: Add service worker with offline support and route caching to web dashboard

- Add offline.html fallback page with gradient background, centered container, and retry button
- Add sw.js service worker with telecom-dashboard-v1 cache for dashboard routes
- Add install event handler caching /, /login, /dashboard, /services, /monitoring, /deploy, /plugins, /automation, /chaos, /billing, and /config routes
- Add fetch event handler with cache-first strategy and offline.html fallback
- Add activate event

apps/web-dashboard/public/sw.js

@@ -0,0 +1,51 @@
+const CACHE_NAME = 'telecom-dashboard-v1';
+const urlsToCache = [
+  '/',
+  '/login',
+  '/dashboard',
+  '/services',
+  '/monitoring',
+  '/deploy',
+  '/plugins',
+  '/automation',
+  '/chaos',
+  '/billing',
+  '/config',
+];
+
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(CACHE_NAME)
+      .then((cache) => {
+        return cache.addAll(urlsToCache);
+      })
+  );
+});
+
+self.addEventListener('fetch', (event) => {
+  event.respondWith(
+    caches.match(event.request)
+      .then((response) => {
+        if (response) {
+          return response;
+        }
+        return fetch(event.request).catch(() => {
+          return caches.match('/offline.html');
+        });
+      })
+  );
+});
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys().then((cacheNames) => {
+      return Promise.all(
+        cacheNames.map((cacheName) => {
+          if (cacheName !== CACHE_NAME) {
+            return caches.delete(cacheName);
+          }
+        })
+      );
+    })
+  );
+});