Bump postcss from 8.5.10 to 8.5.18

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.10 to 8.5.18.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss/compare/8.5.10...8.5.18)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.18
  dependency-type: direct:development
...

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

package.json

@@ -27,7 +27,7 @@
     "@types/react-dom": "^18.3.0",
     "eslint": "^10.6.0",
     "eslint-config-next": "16.2.10",
-    "postcss": "^8.5.10",
+    "postcss": "^8.5.18",
     "tailwindcss": "^3.4.12",
     "typescript": "^5.6.2"
   }