[PVE-User] shutdown and stay shut

[Randy Bush]

debian bookworm
proxmox 8.4.14

we are going perform some complex surgery on a cluster.  so we want to
shut proxmox down and have it stay down across a few power up and down
cycles aided by the usual `shutdown -[hr] now` etc.

what is the best way to tell proxmox not to come back up and start vms
on reboot / power-up?  there seems to be no

    sudo systemctl disable proxmox.service

ddg gives me a million hits for disabling the no subscription notice :)

thanks for clues

randy