Replace torchaudio.load with soundfile.read (bypasses torchcodec requirement)

Remove torchcodec (CUDA-only), use soundfile backend for all torchaudio.load calls

Fix NoneType error when ref_text is not provided

Remove show_api param (not supported in Gradio 6.x)

CPU Basic version: removed spaces.GPU, forced CPU/float32, trimmed deps, whisper-small