Support Vite 7 - Failed compatibility check

When trying to upgrade our dependencies at [MaMpf](https://github.com/mampf-hd/mampf), we faced [this error](https://github.com/MaMpf-HD/mampf/actions/runs/22916758983/job/66504134658?pr=1068#step:5:996):

```
ERROR -- : Failed to check mode for Vite: vite-plugin-ruby@^5.1.0 might not be compatible with vite_ruby-3.9.3

You may disable this check if needed: https://vite-ruby.netlify.app/config/#skipcompatibilitycheck

You may upgrade both by running:

bundle exec vite upgrade

bin/rails aborted!
```

This error occurs with:

- Gem: `vite_ruby: 3.9.3`
- Npm package: `vite-plugin-ruby: 5.1.3`

`bundle exec vite upgrade` changes the `package.json` from `vite@^7.0.0` to `vite@^6.2.6`, resolving to version `6.4.1`, which was [released](https://github.com/vitejs/vite/releases/tag/v6.4.1) October 20, 2025. Given that Vite 8 is already in Beta, I'd love to see support for Vite 7 for the awesome vite_ruby😊 We were already using Vite 7 in production, but just faced this issue now during the update.