List aggregated TTS voices

curl --request GET \
  --url https://api.vatel.ai/v1/voices \
  --header 'Authorization: Bearer <token>'

{
  "voices": [
    {
      "id": "<string>",
      "name": "<string>",
      "provider": "elevenlabs",
      "languages": [
        "<string>"
      ],
      "description": "<string>",
      "preview_url": "<string>",
      "featured": true
    }
  ]
}