POST /tts/generate — Submit single TTS job
POST /tts/batch — Submit batch (up to 500)
GET /tts/status/:jobId — Job status
GET /tts/batch/:batchId — Batch status
GET /tts/download/:jobId — Download WAV
DELETE /tts/job/:jobId — Delete job
GET /tts/voices — List voices
GET /health — Health check