Replace Bad Gateway page on server with a more user-friendly note

[fbanados]

When the server has some issue (e.g. it stops processing requests) it generally produces a 502 bad gateway error.

It would be useful to have some feedback page saying that it's a problem on the server side (something like "Woops, there's a problem with the altlab server!") and add a contact email for when these errors happen.

[fbanados]

Something like

ᓇᔦᐦᑖᐏᐸᔨᐣ
"There is a problem with the computers at the University of Alberta that make this website work. Please check status.altlab.dev for updates."

Of course we would need to set up that status.altlab.dev website as well if we add that sentence.