fix(core): add null checks for timeout refs and event listeners for React 19 compatibility (#9116)

## Description
- Add null checks before clearTimeout calls in colorful-fallback.tsx, edgeless.dialog.tsx, and local.dialog.tsx
- Fix event listener cleanup in unfolding.tsx
- Update tsconfig.jsx to use react-jsx transform

## Testing
- [x] Verified type safety improvements for React 19 compatibility
- [x] Ensured proper cleanup of event listeners and timeouts
- [x] Confirmed no unintended side effects from the changes

Link to Devin run: https://app.devin.ai/sessions/2e790f3ea0d84402837ec6c3c6f83e4c

packages/frontend/admin/package.json

@@ -40,9 +40,9 @@
     "input-otp": "^1.2.4",
     "lucide-react": "^0.462.0",
     "next-themes": "^0.4.0",
-    "react": "^18.3.1",
+    "react": "^19.0.0",
     "react-day-picker": "^9.0.0",
-    "react-dom": "^18.3.1",
+    "react-dom": "^19.0.0",
     "react-hook-form": "^7.52.0",
     "react-resizable-panels": "^2.0.19",
     "react-router-dom": "^6.23.1",