Transcribe audio to text using OpenAI Whisper.

Body: audio: Audio file (webm, mp3, wav, mp4, ogg)

Returns: {"text": "transcribed text"}

Errors: 400: Invalid audio format or empty file 413: File too large (max 10 MB) 429: Rate limit exceeded 500: Transcription failed

Rate limits: - 15 requests/hour per IP - 30 requests/hour per session

Example: const formData = new FormData(); formData.append('audio', audioBlob, 'recording.webm'); const res = await fetch('/api/stt/transcribe', { method: 'POST', body: formData }); const {text} = await res.json();