Use reliable official Blender mirror in Dockerfile

Fix Blender download User-Agent in Dockerfile

Fix EXT_texture_webp GLB import error in Blender by upgrading to Blender 4.2 LTS and sanitizing glTF extension headers

Add missing shared X11/GUI libraries to Dockerfile to fix Blender exit status 127 in Hugging Face Space

Update Dockerfile dependency copies, folder generation, and entry point CMD for the backend/ restructure

Fix generated folder permissions

Fix Hugging Face port and user permissions

Fix HF Space port and user permissions

Fix Dockerfile dependencies for Debian

Initial deploy