- Add mmx64.efi (MOK Manager) to EFI/BOOT/ for Secure Boot enrollment
- Add ENROLL_THIS_KEY_IN_MOKMANAGER.cer to tool/ for key enrollment
- Replace Ventoy background.png with hiperiso-branded one (dark navy
background, green 'hiperiso' title, 'Hypervisor ISO Boot Tool' subtitle)
- Verified via QEMU+OVMF boot test: GRUB2 boots, passes all validation
checks, shows hiperiso menu with correct branding, zero Ventoy refs
