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.electron.mts

@@ -20,8 +20,7 @@
  * 
  * Environment Variables:
  * - VITE_PLATFORM: Set to "electron"
- * - VITE_PWA_ENABLED: Disabled for desktop
- * - VITE_DISABLE_PWA: Enabled for desktop
+ * - PWA: Disabled for desktop (via build exclusion)
  */
 
 import { defineConfig } from "vite";
@@ -140,8 +139,8 @@ export default defineConfig(async () => {
     define: {
       ...baseConfig.define,
       'process.env.VITE_PLATFORM': JSON.stringify('electron'),
-      'process.env.VITE_PWA_ENABLED': JSON.stringify(false),
-      'process.env.VITE_DISABLE_PWA': JSON.stringify(true),
+
+      
       // Electron-specific flags
       '__ELECTRON__': JSON.stringify(true),
       '__IS_DESKTOP__': JSON.stringify(true),