Bump postcss from 8.5.16 to 8.5.18 in /jeecgboot-vue3

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.16 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/8.5.16...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>

jeecgboot-vue3/package.json

@@ -140,7 +140,7 @@
     "lint-staged": "15.2.2",
     "npm-run-all": "^4.1.5",
     "picocolors": "^1.1.1",
-    "postcss": "^8.5.16",
+    "postcss": "^8.5.18",
     "postcss-html": "^1.8.1",
     "postcss-less": "^6.0.0",
     "prettier": "^3.9.5",