[enhancement]: Shuttle Jaguar as a starter model (FLUX, Apache-licensed)

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Contact Details

_No response_

### What should this feature add?

Nominating [Shuttle Jaguar](https://huggingface.co/shuttleai/shuttle-jaguar) as a Starter Model.

Fast (four-step), Apache licensed, quantized versions available, hosted on 🤗. I suggest including the Q_6 as an alternative to Schnell appropriate for mid-range devices.

It's definitely distinct enough from Schnell to be worth checking out. Reasonably versatile even if there are of course some weak spots.

### Alternatives

There's also its predecessor, [Shuttle 3 Diffusion](https://huggingface.co/shuttleai/shuttle-3-diffusion).

### Additional Content

_No response_