build(deps): bump postcss from 8.5.15 to 8.5.25 in /src/frontend

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.15 to 8.5.25.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.15...8.5.25)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.25
  dependency-type: direct:production
...

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

Author: dependabot[bot]

src/frontend/package-lock.json

@@ -31,7 +31,7 @@
     "lucide-react": "^1.7.0",
     "mermaid": "^11.15.0",
     "messagebar": "^0.2.1",
-    "postcss": "^8.5.8",
+    "postcss": "^8.5.25",
     "react": "^19.2.4",
     "react-dom": "^19.2.4",
     "react-dropzone": "^15.0.0",