Bump vitest from 2.1.6 to 2.1.9 in /frontend

Bumps [vitest](https://github.com/vitest-dev/vitest/tree/HEAD/packages/vitest) from 2.1.6 to 2.1.9.
- [Release notes](https://github.com/vitest-dev/vitest/releases)
- [Commits](https://github.com/vitest-dev/vitest/commits/v2.1.9/packages/vitest)

---
updated-dependencies:
- dependency-name: vitest
  dependency-type: direct:development
...

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

frontend/package.json

@@ -80,7 +80,7 @@
     "tailwindcss": "^3.4.9",
     "typescript": "^5",
     "vite-tsconfig-paths": "^5.1.3",
-    "vitest": "^2.1.6"
+    "vitest": "^2.1.9"
   },
   "overrides": {
     "@types/react": "npm:types-react@19.0.0-rc.1",