Bump eslint from 9.23.0 to 9.28.0 in /frontend

Bumps [eslint](https://github.com/eslint/eslint) from 9.23.0 to 9.28.0.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/main/CHANGELOG.md)
- [Commits](https://github.com/eslint/eslint/compare/v9.23.0...v9.28.0)

---
updated-dependencies:
- dependency-name: eslint
  dependency-version: 9.28.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

frontend/package.json

@@ -21,7 +21,7 @@
 	},
 	"devDependencies": {
 		"concurrently": "^9.1.2",
-		"eslint": "9.23.0",
+		"eslint": "9.28.0",
 		"eslint-plugin-unused-imports": "^4.1.4",
 		"npm-check-updates": "^17.1.16",
 		"prettier": "^3.5.3",