fix(frame): set root for deployment and add Linux group handling

[brizzbuzz]

• Change deployment target user to root for remote host deployments to
  allow system-level operations during provisioning.
• Ensure generated Linux user entries include a primary group per user:
  set mkLinuxUser.group to the username and generate users.groups for
  Linux hosts so group records exist alongside users.
• Update flake.lock with multiple dependency bumps and add a new
  authentik-go node; refreshes narHashes, revisions, and timestamps.
• Document an alternative direct flake install workflow and post-reboot
  checklist in initial system setup notes to simplify installs and
  remind operators to set passwords for defined users.

These changes fix missing group definitions for NixOS-managed users,
enable root-based deployment workflows, and keep flake inputs up to
date for reproducible builds.