First of all this patch moves the CSS code into an own scss file.
Further this change also switches from hiding the form completely, to
put an overlay over the form while crypto is loaded and verified as well
as when an error appears. This should make sure, that users don't run
into problems while looking a big nicer than suddenly displaying a text
like it was there all the time.

It's still not perfect, but slowly improving in usability. Next step is
to do some more usability testing with people who are willing to send me
funny emails.