Make MLXLLM compilable on Linux

[gmondada]

Proposed changes

Make this package compilable on Linux.

Not all modules (targets) can be compiled on Linux. MLXVLM, for instance, has no Linux implementation yet.

Please note that, from a multi-platform perspective, UserInput.Image and UserInput.Video are very good. However, UserInput.VideoFrame is not suitable for a multi-platform environment. Therefore, I'm proposing to deprecate the UserInput.VideoFrame.frame property and replace it by UserInput.VideoFrame.image.

This will allow, in the future, to create a MediaProcessor which uses UserInput.Image instead of CIImage, making abstraction of the native API being used.

Checklist

• I have read the CONTRIBUTING document
• I have run pre-commit run --all-files to format my code / installed pre-commit prior to committing changes
• I have added tests that prove my fix is effective or that my feature works
• I have updated the necessary documentation (if needed)

[gmondada]

@Joannis 👆