chore(deps): Bump postcss in /src/frontend in the npm-minor-patch group

Bumps the npm-minor-patch group in /src/frontend with 1 update: [postcss](https://github.com/postcss/postcss).


Updates `postcss` from 8.5.30 to 8.5.31
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.30...8.5.31)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.31
  dependency-type: direct:development
  update-type: version-update:semver-patch
  dependency-group: npm-minor-patch
...

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

Author: dependabot[bot]

src/frontend/package-lock.json

@@ -50,7 +50,7 @@
     "@types/node": "^22.20.5",
     "autoprefixer": "^10.6.1",
     "jsdom": "^27.4.0",
-    "postcss": "^8.5.30",
+    "postcss": "^8.5.31",
     "tailwindcss": "^3.4.19",
     "typescript": "~5.9.3",
     "vitest": "^4.1.12"