chore: Bump the npm-version-updates group in /frontend with 2 updates

Bumps the npm-version-updates group in /frontend with 2 updates: [postcss-html](https://github.com/ota-meshi/postcss-html) and [stylelint](https://github.com/stylelint/stylelint).


Updates `postcss-html` from 1.7.0 to 1.8.0
- [Release notes](https://github.com/ota-meshi/postcss-html/releases)
- [Commits](ota-meshi/postcss-html@v1.7.0...v1.8.0)

Updates `stylelint` from 16.13.1 to 16.13.2
- [Release notes](https://github.com/stylelint/stylelint/releases)
- [Changelog](https://github.com/stylelint/stylelint/blob/main/CHANGELOG.md)
- [Commits](stylelint/stylelint@16.13.1...16.13.2)

---
updated-dependencies:
- dependency-name: postcss-html
  dependency-type: direct:development
  update-type: version-update:semver-minor
  dependency-group: npm-version-updates
- dependency-name: stylelint
  dependency-type: direct:development
  update-type: version-update:semver-patch
  dependency-group: npm-version-updates
...

Signed-off-by: dependabot[bot] <[email protected]>

frontend/package.json

@@ -30,8 +30,8 @@
     "flush-promises": "^1.0.2",
     "jest-serializer-vue-tjw": "^3.20.0",
     "jsdom": "^25.0.1",
-    "postcss-html": "^1.7.0",
-    "stylelint": "^16.13.1",
+    "postcss-html": "^1.8.0",
+    "stylelint": "^16.13.2",
     "stylelint-config-recommended-vue": "^1.5.0",
     "stylelint-config-standard": "^36.0.1",
     "vite": "^6.0.7",