fix(deps): bump tailwindcss from 4.1.11 to 4.2.1 in /frontend

Bumps [tailwindcss](https://github.com/tailwindlabs/tailwindcss/tree/HEAD/packages/tailwindcss) from 4.1.11 to 4.2.1.
- [Release notes](https://github.com/tailwindlabs/tailwindcss/releases)
- [Changelog](https://github.com/tailwindlabs/tailwindcss/blob/main/CHANGELOG.md)
- [Commits](https://github.com/tailwindlabs/tailwindcss/commits/v4.2.1/packages/tailwindcss)

---
updated-dependencies:
- dependency-name: tailwindcss
  dependency-version: 4.2.1
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

frontend/package-lock.json

@@ -42,7 +42,7 @@
     "@types/react-dom": "^19.1.2",
     "@types/ws": "^8.18.1",
     "cross-env": "^7.0.3",
-    "tailwindcss": "^4.1.4",
+    "tailwindcss": "^4.2.1",
     "tsx": "^4.21.0",
     "typed-css-modules": "^0.9.1",
     "typescript": "^5.9.3",