v2.7.4

Adds in-app MBR to GPT conversion for selected USB targets.\n\nThe app can now erase an MBR USB, convert it to GPT, and leave behind a FAT32 OPENCORE volume instead of forcing a manual shell step first. Existing OPENCORE reuse is also now limited to disks that already report GPT, so an MBR disk cannot slip through on label alone.