Fix: set sdk_version=5.50.0 (gradio 5.x compatible with huggingface_hub 1.x)

Fix: upgrade to gradio 5.x (HfFolder removed in huggingface_hub 1.x)

Fix: use audioop-lts (not pyaudioop) for Python 3.13

Fix Python 3.13 audioop removal: add pyaudioop

Add requirements.txt