build(deps-dev): bump postcss from 8.5.4 to 8.5.6

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.4 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@8.5.4...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

@@ -25,7 +25,7 @@
     "autoprefixer": "^10.4.21",
     "eslint": "^9.28.0",
     "eslint-plugin-svelte": "^3.9.1",
-    "postcss": "^8.5.4",
+    "postcss": "^8.5.6",
     "prettier": "^3.5.3",
     "prettier-plugin-tailwindcss": "^0.6.14",
     "svelte": "^5.33.16",