Refactor demo to use new ServiceHost and ServiceClient API

- Update to @xtr-dev/rondevu-client v0.10.1
- Replace Rondevu class with RondevuService, ServiceHost, ServiceClient
- Simplify demo implementation (removed complex features)
- Use new event-driven API for connections
- Support custom RTC configuration
- Backup old implementation as App-old.jsx

Breaking changes from v1 API:
- RondevuService for username claiming
- ServiceHost for hosting services with offer pool
- ServiceClient for connecting with auto-reconnection

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

package.json

@@ -10,7 +10,7 @@
     "deploy": "npm run build && npx wrangler pages deploy dist --project-name=rondevu-demo"
   },
   "dependencies": {
-    "@xtr-dev/rondevu-client": "^0.10.0",
+    "@xtr-dev/rondevu-client": "^0.10.1",
     "@zxing/library": "^0.21.3",
     "qrcode": "^1.5.4",
     "react": "^18.2.0",