fix: pin gradio==6.13.0 + hf_hub>=1.0 (verified compatible locally; gradio 5.6 + hf_hub 1.x had HfFolder import error)

fix: pin Python 3.12 + upgrade Gradio to 5.6 (Python 3.13 broke pydub via audioop removal)

Initial demo: side-by-side fill-mask comparison vioBERT-v3 vs MARBERTv2

initial commit