Enable users to listen to their song while video generation continues
in the background. Backend proxies authenticated Sonauto stream API
since HTML audio elements cannot send auth headers.
- Add streaming_ready_at column to track when stream becomes available
- Enable streaming in Sonauto API request payload
- Handle GENERATING_STREAMING_READY webhook status
- Add /api/stream/{session_id} proxy endpoint using httpx
- Update StatusResponse with streaming_ready and task_id fields
- Add audio player UI with autoplay fallback for mobile
- Fade out audio gracefully before redirect to result page
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
