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.

experiment.sh

@@ -92,8 +92,8 @@ rm -rf dist* || log_warn "No previous builds to clean"
 # Set environment variables for the build
 log_info "Configuring build environment..."
 export VITE_PLATFORM=electron
-export VITE_PWA_ENABLED=false
-export VITE_DISABLE_PWA=true
+
+
 export DEBUG_MIGRATIONS=0
 
 # Ensure TypeScript is installed