Migrate from `cnfast` to `cn`

Hi,

I know it's only been 3 months since project moved away from `clsx` + `tailwind-merge` to `cnfast` (#597) but @shadcn and @aidenybai (author of `cnfast` btw) just open sourced `cn` which is even faster than `cnfast` 😄

More info here: https://www.npmjs.com/package/cn
and here: https://github.com/shadcn-ui/cn

It's as simple as replacing `cnfast` dependency and references with `cn` and keeping everything else the same. Tried locally, and it builds. Can submit a PR for it if you consider touching the very same thing in 3 months apart.

Cheers,
G.

Start by locating the cnfast dependency and its references in the project, then review the linked cn package information. The work is done when those references use cn instead, everything else remains unchanged, and the project builds successfully.

Written by the indexing model from the issue text.