Replaces manual first-boot installer injection with a Cloud-Init user-data configuration for fully automated UniFi OS Server setup. Cloud-Init is now always enabled and required, simplifying image preparation and installation monitoring. Updates messaging and installation flow to reflect Cloud-Init usage and removes legacy non-Cloud-Init support.
Update the logic for detecting errors during base package pre-installation in unifi-os-server-vm.sh by checking for 'error' in the output. Also correct URLs in cloud-init.func to use the correct repository path.
