An overdue claim whose reminder had already been sent, with that reminder's own
payment deadline still running, fell through to the plain "überfällig" error
finding whenever reminder_due's escalation check returned None to signal "not
yet time for the next Mahnstufe" -- that None was indistinguishable from "never
handled at all" to the caller, so it looked neglected even though a reminder was
already out. Give that case its own low-priority "reminder_awaiting_deadline"
finding instead of silently falling back to the overdue-error path.
Birthday and membership-anniversary findings also kept firing for members whose
status is "ended", which doesn't make sense once the membership itself is over.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>