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/core/package.json

@@ -65,8 +65,8 @@
     "nanoid": "^5.0.7",
     "next-themes": "^0.4.0",
     "query-string": "^9.1.0",
-    "react": "18.3.1",
-    "react-dom": "18.3.1",
+    "react": "19.0.0",
+    "react-dom": "19.0.0",
     "react-error-boundary": "^4.0.13",
     "react-router-dom": "^6.22.3",
     "react-transition-state": "^2.1.1",
@@ -81,7 +81,9 @@
     "zod": "^3.22.4"
   },
   "devDependencies": {
-    "@testing-library/react": "^16.0.0",
+    "@swc/core": "^1.9.3",
+    "@testing-library/dom": "^9.3.4",
+    "@testing-library/react": "^16.1.0",
     "@types/animejs": "^3.1.12",
     "@types/bytes": "^3.1.4",
     "@types/image-blob-reduce": "^4.1.4",