Only allow Lox (invites) in alpha and nightly builds
We should add some kind of guard to prevent Lox invites for the stable 13.5 release.
I imagine we could use a preference. In terms of the UI, I think we only need to change one line to disallow Lox invites in the "Add new bridges" dialog.
Do we also want some extra safety checks in other places to prevent the Lox module from doing anything?