feat: integrate PWA functionality with platform service architecture

- Add PWA methods to PlatformService interface (registerServiceWorker, isPWAEnabled)
- Implement PWA logic in WebPlatformService with service worker registration
- Add no-op PWA implementations for Capacitor and Electron platforms
- Create PWAInstallPrompt component with custom install UI and event handling
- Integrate PWA components into App.vue with platform-aware conditional rendering
- Ensure PWA features only load on web platform via platform service pattern
- Centralize PWA logic in platform service for consistent cross-platform behavior
- Add comprehensive PWA documentation and installation flow support

Platform service now handles all PWA operations including service worker
registration, install prompts, and platform-specific feature detection.

src/App.vue

@@ -2,7 +2,7 @@
   <router-view />
 
   <!-- PWA Install Prompt -->
-  <PWAInstallPrompt />
+  <PWAInstallPrompt v-if="isPWAEnabled" />
 
   <!-- Messages in the upper-right - https://github.com/emmanuelsw/notiwind -->
   <NotificationGroup group="alert">
@@ -338,6 +338,7 @@ import { NotificationIface } from "./constants/app";
 import { PlatformServiceMixin } from "@/utils/PlatformServiceMixin";
 import { logger } from "./utils/logger";
 import PWAInstallPrompt from "@/components/PWAInstallPrompt.vue";
+import { PlatformServiceFactory } from "@/services/PlatformServiceFactory";
 
 interface Settings {
   notifyingNewActivityTime?: string;
@@ -355,6 +356,18 @@ export default class App extends Vue {
 
   stopAsking = false;
 
+  get isPWAEnabled() {
+    return PlatformServiceFactory.getInstance().isPWAEnabled;
+  }
+
+  mounted() {
+    // Register service worker only if PWA is enabled
+    const platformService = PlatformServiceFactory.getInstance();
+    if (platformService.isPWAEnabled && platformService.registerServiceWorker) {
+      platformService.registerServiceWorker();
+    }
+  }
+
   // created() {
   //   logger.log(
   //     "Component created: Reactivity set up.",