Production-ready Hunyuan3D-2.1 PBR pipeline + Unity glTFast integration

fix: use_safetensors=False in shape pipeline

fix: use_safetensors=False (weights are .ckpt format)

fix: Hunyuan3D-2.1 subfolders + cache symlink for shape+texture

fix: Hunyuan3D-2.1 subfolder hunyuan3d-dit-v2-1 + cache symlink

fix: huggingface-cli deprecated → use hf download

fix: add libopengl0+libegl1+libxcb-cursor0 to avoid pymeshlab plugin warnings

fix: Ubuntu 24.04 compat (libgl1-mesa-glx → libgl1, libglib2.0-0 → libglib2.0-0t64 fallback)

Initial pipeline scaffold: Hunyuan3D-2.1 + ComfyUI on Vast.ai