feat: add virtual environment support for ComfyUI

Changes:
- Create venv for ComfyUI in setup/comfyui-base script
- Install extension dependencies: GitPython, opencv-python-headless,
  diffusers, insightface, onnxruntime
- Update start.sh to activate venv before running
- Add musicgen model directory

This fixes import errors for custom nodes:
- ComfyUI-Manager (needs GitPython)
- ComfyUI-Impact-Pack (needs opencv)
- ComfyUI-VideoHelperSuite (needs opencv)
- ComfyUI-CogVideoXWrapper (needs diffusers)
- ComfyUI-Inspire-Pack (needs insightface, onnxruntime)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

comfyui/start.sh

@@ -16,12 +16,20 @@ export TQDM_DISABLE=1
 # Navigate to ComfyUI directory
 cd "${COMFYUI_DIR}" || exit 1
 
+# Activate virtual environment
+if [ -d "venv" ]; then
+  echo "Activating ComfyUI virtual environment..."
+  source venv/bin/activate
+else
+  echo "WARNING: venv not found, using system Python"
+fi
+
 echo "Starting ComfyUI on port 8188..."
 echo "Access at: http://localhost:8188"
 echo "Using HuggingFace cache: ${HF_CACHE}"
 
 # Start ComfyUI with GPU support
-python3 main.py \
+python main.py \
   --listen 0.0.0.0 \
   --port 8188 \
   --enable-cors-header \