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/components/PWAInstallPrompt.vue

@@ -59,6 +59,7 @@
 <script lang="ts">
 import { Component, Vue } from "vue-facing-decorator";
 import { logger } from "@/utils/logger";
+import { PlatformServiceFactory } from "@/services/PlatformServiceFactory";
 
 interface BeforeInstallPromptEvent extends Event {
   prompt(): Promise<void>;
@@ -67,11 +68,13 @@ interface BeforeInstallPromptEvent extends Event {
 
 @Component({ name: "PWAInstallPrompt" })
 export default class PWAInstallPrompt extends Vue {
+  $notify!: (notification: any, timeout?: number) => void;
   private showInstallPrompt = false;
   private deferredPrompt: BeforeInstallPromptEvent | null = null;
   private dismissed = false;
 
   mounted() {
+    if (!PlatformServiceFactory.getInstance().isPWAEnabled) return;
     this.setupInstallPrompt();
   }