build(deps): bump undici and @sveltejs/kit in /app

Bumps [undici](https://github.com/nodejs/undici) to 5.28.4 and updates ancestor dependency [@sveltejs/kit](https://github.com/sveltejs/kit/tree/HEAD/packages/kit). These dependencies need to be updated together.


Updates `undici` from 5.20.0 to 5.28.4
- [Release notes](https://github.com/nodejs/undici/releases)
- [Commits](nodejs/undici@v5.20.0...v5.28.4)

Updates `@sveltejs/kit` from 1.15.4 to 1.30.4
- [Release notes](https://github.com/sveltejs/kit/releases)
- [Changelog](https://github.com/sveltejs/kit/blob/@sveltejs/[email protected]/packages/kit/CHANGELOG.md)
- [Commits](https://github.com/sveltejs/kit/commits/@sveltejs/[email protected]/packages/kit)

---
updated-dependencies:
- dependency-name: undici
  dependency-type: indirect
- dependency-name: "@sveltejs/kit"
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>