npm-dep: bump tailwindcss from 4.0.15 to 4.0.16 in /frontend

Bumps [tailwindcss](https://github.com/tailwindlabs/tailwindcss/tree/HEAD/packages/tailwindcss) from 4.0.15 to 4.0.16.
- [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/v4.0.16/packages/tailwindcss)

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

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

frontend/package.json

@@ -33,7 +33,7 @@
 		"prettier-plugin-tailwindcss": "^0.6.11",
 		"svelte": "^5.25.3",
 		"svelte-check": "^4.1.5",
-		"tailwindcss": "^4.0.15",
+		"tailwindcss": "^4.0.16",
 		"tslib": "^2.8.1",
 		"typescript": "^5.8.2",
 		"typescript-eslint": "^8.28.0",