frontend: bump typescript-eslint from 8.13.0 to 8.21.0 in /frontend

Bumps [typescript-eslint](https://github.com/typescript-eslint/typescript-eslint/tree/HEAD/packages/typescript-eslint) from 8.13.0 to 8.21.0.
- [Release notes](https://github.com/typescript-eslint/typescript-eslint/releases)
- [Changelog](https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/typescript-eslint/CHANGELOG.md)
- [Commits](https://github.com/typescript-eslint/typescript-eslint/commits/v8.21.0/packages/typescript-eslint)

---
updated-dependencies:
- dependency-name: typescript-eslint
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

frontend/package.json

@@ -42,7 +42,7 @@
 		"globals": "^15.11.0",
 		"prettier": "^3.3.3",
 		"typescript": "^5.6.3",
-		"typescript-eslint": "^8.13.0",
+		"typescript-eslint": "^8.21.0",
 		"vite": "^5.4.10"
 	},
 	"lint-staged": {