Bump flat from 5.0.0 to 5.0.1 in /server

Bumps [flat](https://github.com/hughsk/flat) from 5.0.0 to 5.0.1.
- [Release notes](https://github.com/hughsk/flat/releases)
- [Commits](hughsk/flat@5.0.0...5.0.1)

---
updated-dependencies:
- dependency-name: flat
  dependency-type: direct:production
...

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