fix: improve vad sensitivity and buffer size for better transcription accuracy

[MusicMaster4]

Summary

• Adjusted VAD sensitivity to retain more speech, improving transcription accuracy for clipped consonants and proper nouns.
• Increased ring buffer size to 12 to preserve more audio around VAD activations.
• Increased beam size and best_of parameters to 8 for more accurate transcription.
• Added patience and condition_on_previous_text parameters to improve transcription quality.
• Increased silence_frames threshold to 18 to better handle longer pauses in speech.