Update build and setup scripts to support both CUDA and ROCm backends

- Setup script now creates both venv-cuda and venv-rocm by default
- Build script builds both CUDA and ROCm worker versions
- Start script reads configuration to launch appropriate backend workers
- Added pip3 detection and --break-system-packages support
- Windows batch files updated with pip3 detection
- Runtime can switch between CUDA/ROCm implementations based on config