feat: add CosyVoice2/3 TTS engine with instruct and voice cloning

Integrate Alibaba's CosyVoice2-0.5B and Fun-CosyVoice3-0.5B as a new
TTS engine supporting 9 languages, zero-shot voice cloning, and instruct
control (emotions, speed, volume, dialects).

The CosyVoice source is cloned at setup time into backend/vendors/ since
no PyPI package exists. A modelscope→HuggingFace shim redirects model
downloads to the public HF repos, and a lightweight pylogger shim avoids
pulling in pytorch-lightning as a transitive dependency.

Backend: cosyvoice_backend.py, __init__.py registry, models.py regex
Frontend: engine selector, language map, Zod schema, model descriptions
Infra: requirements.txt, justfile, release.yml, Dockerfile, PyInstaller

app/src/components/ServerSettings/ModelManagement.tsx

@@ -66,6 +66,10 @@ const MODEL_DESCRIPTIONS: Record<string, string> = {
     'HumeAI TADA 1B — English speech-language model built on Llama 3.2 1B. Generates 700s+ of coherent audio with synchronized text-acoustic alignment.',
   'tada-3b-ml':
     'HumeAI TADA 3B Multilingual — built on Llama 3.2 3B. Supports 10 languages with high-fidelity voice cloning via text-acoustic dual alignment.',
+  'cosyvoice2-0.5b':
+    'CosyVoice2 0.5B by Alibaba. Multilingual TTS with instruct support for emotions, speed, volume, and dialects. 9 languages with zero-shot voice cloning.',
+  'cosyvoice3-0.5b':
+    'Fun-CosyVoice3 0.5B by Alibaba. Improved robustness, prosody, and Chinese dialect support over CosyVoice2. Best quality for in-the-wild speech generation.',
   'whisper-base':
     'Smallest Whisper model (74M parameters). Fast transcription with moderate accuracy.',
   'whisper-small':