Fetch the provisioning agent from git.tuxflotte.de, register it via
POST /api/v1/agent/bootstrap using the device id from the activation
response, write /etc/tuxflotte/agent.credentials, and enable the
tuxflotte-agent systemd service so it starts on first boot. Verified
end to end against a QEMU test VM and the real anode API.
The device id is now threaded through backend_generate_config() and
substituted into the kickstart template like the existing hostname
and blueprint values. %post drops the implicit chroot-wide set -e in
favor of per-step error handling, since localectl calls in this
section are known to fail best-effort without a running D-Bus.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>