the backend code has been added back in, and the build process has been
modified so that no output files are left outside of build/. Admin page
loads and logs in correctly, nothing else functionality-wise yet.
Hyphens are added to user IDs from 10.7.0, so if the server is running
it, emails.json will be modified to include them. The existing file is
backed up. Also, scss files have been simplified since bs4-jf and bs5-jf share
much of the same content.