curl --request POST \
  --url https://geoff.ai/api/v1/voice/isolate \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
    "audio_url": "https://files.geoff.ai/music/track.mp3",
    "return_instrumental": true,
    "format": "wav"
  }'

{
  "data": {
    "vocals_url": "https://files.geoff.ai/output/vocals_abc123.wav",
    "vocals_b64": "...",
    "instrumental_url": "https://files.geoff.ai/output/instrumental_abc123.wav",
    "instrumental_b64": "...",
    "format": "wav",
    "sample_rate": 44100,
    "duration_s": 187.4
  },
  "trace_id": "04ede0ab069fb1ba8be5156a24b1e081"
}