dev gained the delivery/rollback semantics for the dunning and SEPA mails while
the mail texts were being moved into templates here. Both services keep dev's
flow -- roll back only while nothing has gone out, log the event even when
archiving fails afterwards -- and render their content from the template.
The welcome mail follows the same rule now, including its archiving-failure
path.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>