Render the infobox on the client side.

This removes a lot of cached crap on the server side, and just generally
makes so much more sense. It makes fullscreen setup a bit slower (though
not that much, thanks to a new covering partial index). Interestingly,
it now more often shows the infobox on mobile, since it no longer cares
about text overflow; it's possible we should try to do something about
that.