fix: enable root SSH login in preseed-bootstrap for debugging

Allows SSH as root during first-boot setup phase so we can run
commands without relying on the Proxmox console for paste.
install-kiosk.sh already disables this after kiosk setup completes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

preseed-bootstrap.sh

@@ -28,6 +28,9 @@ if [ -x /usr/local/bin/kiosk-setup ]; then
 fi
 EOF
 
+# Allow root SSH login for debugging during setup
+sed -i 's/^#\?PermitRootLogin.*/PermitRootLogin yes/' /etc/ssh/sshd_config
+
 # Boot to text mode for the setup wizard
 systemctl set-default multi-user.target