uv installation shenanigans

[anantshri]

We have requirements-uv.txt

but we are still directly installing it in buildscripts

https://github.com/cyfinoid/keychecker/blob/main/.github/workflows/ci.yml#L24
https://github.com/cyfinoid/keychecker/blob/main/.github/workflows/publish.yml#L39
https://github.com/cyfinoid/keychecker/blob/main/.github/workflows/publish.yml#L71

This should ideally be abstracted out to pip install of uv with hashes and then the #1 kind of requests would make sense to update