confirm and adminConfirm now create REQUESTED VisaApplication rows for
every attendee with needsVisa=true, in the same Prisma transaction as
the AttendingMember inserts. editAttendees was extended into a fully
diff-aware sync: existing attendees whose needsVisa flips on get a new
VisaApp; flipping off deletes it; staying true preserves the row (and
its status / notes / dates). Removed attendees cascade automatically
via the FK.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
