Add token alias for Whisper model loading

[bobsummerwill]

Summary

Adds a token alias to whisperx.asr.load_model() while preserving the existing use_auth_token argument for backward compatibility.

Why

WhisperX has already migrated its pyannote-facing code to token, but the ASR model-loading surface still exposed use_auth_token.

The remaining internal use still needs to be forwarded to faster-whisper, whose current WhisperModel API expects use_auth_token.

This change updates the WhisperX API surface to accept token consistently without breaking the downstream faster-whisper call.

Changes

• add token as the preferred alias in whisperx.asr.load_model()
• keep use_auth_token as a legacy alias for backward compatibility
• raise a ValueError if both are passed with conflicting values
• update whisperx/transcribe.py to pass token=hf_token

Validation

• python3 -m py_compile whisperx/asr.py whisperx/transcribe.py

Fixes #1406