chore(deps-dev): bump postcss from 8.5.14 to 8.5.18

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.14 to 8.5.18.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.14...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>

Author: dependabot[bot]

package.json

@@ -29,7 +29,7 @@
     "eslint": "^9.39.2",
     "eslint-config-next": "16.2.6",
     "jsdom": "^29.1.1",
-    "postcss": "^8.5.10",
+    "postcss": "^8.5.18",
     "tailwindcss": "^4.3.0",
     "typescript": "^5.9.3",
     "vitest": "^4.1.6"