Remove manual service worker registration; rely on VitePWA auto-registration

- Deleted src/registerServiceWorker.ts and all related imports
- Cleaned up WebPlatformService and main.web.ts to remove manual SW logic
- Updated VitePWA config for correct dev/prod SW handling
- Fixed missing FontAwesome download icon in PWA prompt
- Updated docs to reflect new PWA registration approach

PWA now works reliably in all web environments with zero manual SW code.

vite.config.web.mts

@@ -88,7 +88,7 @@ export default defineConfig(async ({ mode }) => {
         // Enable PWA in all web environments for consistent testing
         devOptions: {
           enabled: true, // ✅ Enable in all environments
-          type: 'module'
+          type: 'classic'
         },
         workbox: {
           cleanupOutdatedCaches: true,