build(deps-dev): bump postcss from 8.5.25 to 8.5.26 in /frontend

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.25 to 8.5.26.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.25...8.5.26)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.26
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

frontend/package-lock.json

@@ -33,7 +33,7 @@
     "autoprefixer": "^10.5.4",
     "esbuild": "^0.28.1",
     "jsdom": "^30.0.0",
-    "postcss": "^8.5.25",
+    "postcss": "^8.5.26",
     "@tailwindcss/postcss": "^4.3.3",
     "tailwindcss": "^4.3.2",
     "typescript": "^7.0.2",