dal-rescue-02 is on a special port and it's hard to find

dal-rescue-02 is the spare/experimentation server for the OOB access server at quintex, dal-rescue-01.

it's hosted in my homelab and, because I have a single IPv4 IP address there, is on a different port (4622).

each new admin eventually tries to connect to it and fails and needs to learn this fact, and then typically either forgets about it and has the trouble again or adds that to their SSH configuration.

this came up again during the tails merge and especially a recent incident (internal DNSSEC failures (#42308 - closed))

we need to fix this, somehow. a few ideas:

1. ship a SSH config file snippet that includes dal-rescue-02 somehow
2. fix anarcat's homelab to have proper IPv6 and make the host IPv6-only
3. tough it up, real admins nmap servers to figure out the right port
4. create an issue to document this so at least a careful admin will find the trick here (done)