[WIP] Reduce deps core

[Blaizzy]

Summary: This PR removes the dependency on torch, torchvision, and transformers by porting the necessary processors directly into mlx-vlm. It also restructures pyproject.toml to support optional installations.

Changes:

• Removed Dependencies: Core installation no longer requires Torch or Transformers.
• New Extras: Added optional flags for [trainer], [server], and [audio].
• Refactoring:
  • Replaced mlx-audio with soundfile.
  • Moved audio imports to be lazy-loaded within functions to avoid crashes for users without audio dependencies.
  • Cleaned up redundant imports in utils.py.
• Docs: Added installation instructions for optional dependencies to the README.

[altaic]

Sort of related, have you considered replacing py-opencv which pulls in a rather hefty set of deps (120+)? It looks like it's currently only used to load and resize the frames of videos.