Critical: Web Root Misdirection & comfy_api ImportError; DWPose Module Error; PyTorch CUDA Version Warning Custom Node Testing

### Custom Node Testing

- [x] I have tried disabling custom nodes and the issue persists (see [how to disable custom nodes](https://docs.comfy.org/troubleshooting/custom-node-issues#step-1%3A-test-with-all-custom-nodes-disabled) if you need help)

### Expected Behavior

1.The frontend should communicate with the backend via the correct API.
2.Custom nodes (DWPose) should load dependencies from the system Python path.
3.The comfy_api module should be recognized as a valid Python package.
4.PyTorch should utilize the latest CUDA toolkit (cu130) for optimal VRAM management.

### Actual Behavior

1.Frontend Communication Failure: The UI renders but fails to fetch data (CORS/Network error). The server log shows the web root incorrectly points to site-packages.
2.DWPose Load Error: The node fails to load with ModuleNotFoundError: No module named 'skimage', despite scikit-image being installed in the user environment.
3.Core ImportError: The server crashes on startup with No module named 'comfy_api' because comfy_api/__init__.py is 0 bytes.
4.PyTorch Warning: The console warns that cu124 is outdated and suggests upgrading to cu130 for Dynamic VRAM support

### Steps to Reproduce

1.Launch ComfyUI 0.20.1.
2.Observe the console output for the web root path and comfy_api import errors.
3.Attempt to load a workflow containing the DWPose node.
4.Check the Python environment for installed packages (pip list).

System Information
ComfyUI Version: 0.20.1
Python Version: 3.13.7
PyTorch Version: 2.6.0+cu124
OS: Windows 11 Pro Build 26200
GPU: NVIDIA RTX 4060 Laptop (8GB VRAM)

### Debug Logs

```powershell
[Prompt Server] web root: C:\Users...\site-packages\comfyui_frontend_package\static
# Error: comfy_api/__init__.py is 0 bytes
Error: No module named 'comfy_api'

# When loading DWPose:
ModuleNotFoundError: No module named 'skimage'
# Note: scikit-image is installed at ...Python313\Lib\site-packages (0.26.0)
```

### Other

Proposed Fixes:
1.Frontend: Reinstall the frontend package: python -m pip install --force-reinstall comfyui-frontend-package.
2.DWPose: Modify main.py to include user site-packages: import site; site.addsitedir(site.getusersitepackages()).
3.Core: Repair the empty comfy_api/__init__.py file.
4,.PyTorch: Upgrade command: pip install --upgrade torch torchvision torchaudio --index-url https://download.pytorch.org/whl/cu130.