Add unit tests

[mark-wiemer]

Please confirm the following.

• I know that NML is in maintenance mode and will only fix critical bugs.
• I know that NML only officially supports Linux.

What version of the NML App are you using?

1.0.0

Describe the bug

Setup Vitest and optionally something in Rust. Test individual functions, integrated components, and end-to-end tests of the UX. Optionally include Playwright if it fits with the repo. Focus on testing apps/app, not any specific package or other project in the apps folder

Steps to reproduce

No response

Expected behavior

No response

Additional context

No response