- Map audio2audio to cover in Gradio args and Python spawn fallback
(audio2audio is not a valid ACE-Step task type, cover is the equivalent)
- Add /demucs-web to Vite proxy so stem extractor opens correctly in Pinokio
(in Pinokio, Vite runs on a dynamic port and /demucs-web was not proxied)
- Expose aceStepUrl in /api/generate/health response for debugging
On Windows, 'localhost' can resolve to IPv6 ::1 instead of IPv4
127.0.0.1, causing ECONNREFUSED when the Vite dev proxy tries to
reach the Express server. Using explicit 127.0.0.1 avoids this.
Fixes#12