ch-6.12.8-kernel-2-20251211

Enable kernel modules and DRM for NVIDIA GPU passthrough

- Enable CONFIG_MODULES for loadable module support
- Enable CONFIG_DRM and CONFIG_DRM_BOCHS (which selects DRM_TTM)
- Add CI steps to build NVIDIA open-gpu-kernel-modules
- Download NVIDIA driver and extract GSP firmware for H100/modern GPUs
- Package kernel modules + firmware as nvidia-modules-x86_64.tar.gz
- Package userspace driver libraries as nvidia-driver-libs-x86_64.tar.gz
  (libcuda.so, libnvidia-ml.so, nvidia-smi, etc. for container injection)