Bump react from 18.3.1 to 19.1.0 in /site

Bumps [react](https://github.com/facebook/react/tree/HEAD/packages/react) from 18.3.1 to 19.1.0.
- [Release notes](https://github.com/facebook/react/releases)
- [Changelog](https://github.com/facebook/react/blob/main/CHANGELOG.md)
- [Commits](https://github.com/facebook/react/commits/v19.1.0/packages/react)

---
updated-dependencies:
- dependency-name: react
  dependency-version: 19.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]