Theme all emails

[kristianvld]

Test all email templates and update them to match our visual theme.

Some email features require the pro license which we do not have. For some of these we could probably find a solution by triggering the emails from itemize.no or some other source using the send api. E.g. the 2FA update emails are pro-only, but since we need to implement the setup of 2FA on the website anyway, we could trigger this manually.