Bump postcss and styled-components in /app/web_ui

Bumps [postcss](https://github.com/postcss/postcss) to 8.5.10 and updates ancestor dependency [styled-components](https://github.com/styled-components/styled-components). These dependencies need to be updated together.


Updates `postcss` from 8.4.49 to 8.5.10
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.4.49...8.5.10)

Updates `styled-components` from 6.1.19 to 6.4.1
- [Release notes](https://github.com/styled-components/styled-components/releases)
- [Commits](https://github.com/styled-components/styled-components/compare/styled-components@6.1.19...styled-components@6.4.1)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.10
  dependency-type: direct:development
- dependency-name: styled-components
  dependency-version: 6.4.1
  dependency-type: indirect
...

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

Author: dependabot[bot]

app/web_ui/package-lock.json

@@ -33,7 +33,7 @@
     "eslint-plugin-svelte": "^3.12.5",
     "jsdom": "^29.0.2",
     "openapi-typescript": "^7.4.1",
-    "postcss": "^8.4.31",
+    "postcss": "^8.5.10",
     "prettier": "^3.0.3",
     "prettier-plugin-svelte": "^3.0.3",
     "svelte": "^4.2.19",