Remove Git LFS

### Is there an existing issue outlining your problem?

- [x] I have searched the existing issues and they do not solve my problem.

### Describe your issue.

As noted in #2294, committing and pushing to the repository currently requires Git LFS to be installed. This, I believe, is only a relic of our prior practice of having preview images for each style. The only remaining image assets should be the three for documentation under https://github.com/catppuccin/userstyles/tree/main/docs/src/assets.

I think it would make sense to remove the Git LFS repository configuration to make contributing easier. We should migrate the remaining LFS assets to plain Git blobs?

Start by inspecting the repository's Git LFS configuration and the three remaining assets under docs/src/assets. Confirm which files are LFS-tracked and how they are referenced, then migrate those assets to ordinary Git blobs and remove the LFS requirement. Done means contributors no longer need Git LFS and the documentation assets remain available.

Written by the indexing model from the issue text.