chore(deps-dev): bump postcss from 8.5.15 to 8.5.18

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.15 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@8.5.15...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]

frontend/package.json

@@ -111,7 +111,7 @@
     "normalize.css": "8.0.1",
     "oxlint": "1.75.0",
     "oxlint-tsgolint": "7.0.2001",
-    "postcss": "8.5.15",
+    "postcss": "8.5.18",
     "sass": "1.70.0",
     "solid-devtools": "0.34.5",
     "solid-js": "1.9.13",