Working React 19 before Compiler integration

🚀 Phase 2 Complete - React 19 Foundation
- React upgraded: 18.2.0 → 19.0.0 ✅
- MUI upgraded: 5 → 6 ✅
- React Router upgraded: 6 → 7 ✅
- All packages updated and working ✅
- Production build: 995KB bundle ✅
- All containers working ✅

Ready for Phase 3: React Compiler integration

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

.env.example

@@ -39,4 +39,10 @@ GROUP_ID=20
 VITE_API_BASE_URL=http://backend:3001/api
 VITE_AUTH0_DOMAIN=your-domain.auth0.com
 VITE_AUTH0_CLIENT_ID=your-client-id
-VITE_AUTH0_AUDIENCE=https://api.motovaultpro.com
+VITE_AUTH0_AUDIENCE=https://api.motovaultpro.com
+
+# External Server Deployment
+# Update these when deploying to external server with custom domain
+FRONTEND_DOMAIN=motovaultpro.com
+FRONTEND_PORT=3000
+# For API calls from external domain, update backend CORS settings