chore(deps): bump react-i18next from 15.7.3 to 16.0.0 in /frontend (#389)

Bumps [react-i18next](https://github.com/i18next/react-i18next) from 15.7.3 to 16.0.0.
- [Changelog](https://github.com/i18next/react-i18next/blob/master/CHANGELOG.md)
- [Commits](https://github.com/i18next/react-i18next/compare/v15.7.3...v16.0.0)

---
updated-dependencies:
- dependency-name: react-i18next
  dependency-version: 16.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

frontend/package.json

@@ -29,7 +29,7 @@
     "react": "^19.2.0",
     "react-dom": "^19.2.0",
     "react-hook-form": "^7.63.0",
-    "react-i18next": "^15.7.3",
+    "react-i18next": "^16.0.0",
     "react-markdown": "^10.1.0",
     "react-router": "^7.9.3",
     "sonner": "^2.0.7",