dep(deps-dev): bump postcss from 8.5.3 to 8.5.6

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.3 to 8.5.6.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.3...8.5.6)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.6
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

package-lock.json

@@ -39,7 +39,7 @@
     "@types/react": "~19.1.6",
     "@types/react-dom": "~19.1.5",
     "geist": "~1.3.1",
-    "postcss": "~8.5.3",
+    "postcss": "~8.5.6",
     "serve": "~14.2.4",
     "tailwindcss": "^4.1.1",
     "typescript": "~5.8.3"