Add arXiv / HF / License badges to model card

Add arXiv link (2605.14231)

Add self-contained preprocess() with per-variant defaults

Rename AudioMosaicSimCLR -> AudioMosaicPretrain

Rename MST -> AudioMosaic in modeling and remove MelSpectrogramTransformer from cards

Initial release: AudioMosaic ViT-B/16 pretrained encoder

initial commit