Fix CosyVoice device mismatch in voice restoration
Technical implementation:
- Add CosyVoiceHandler.partially_load() for proper device reload
- Update base_wrapper.model_load() to use handler's partially_load()
- Move all CosyVoice components (llm, flow, hift, campplus) with nested modules
- Simplify CosyVoice engine wrapper device management (delegate to handler)
- Add CosyVoice variant setting for <restore> tags (RL/standard options)
- Update settings UI and API endpoint for variant selection
Fixes device tensor mismatch errors when TTS and VC restoration run sequentially
and prevents unnecessary model unload/reload when variants match.
diodiogod
a2e11108e2