When subscriptions moved to the plan model the span became start + end dates,
which lost the simple "renew for N months/weeks/days" input — the operator had
to hand-compute the end date. (quantity is CARS, a separate axis, not periods.)
Add a count field to the sell form: the operator types e.g. 3, and validTo is
auto-derived as validFrom + count × the plan's period (day/week/month), with the
same month-overflow clamp the server uses (Jan 31 +1mo → Feb 28) so the preview
matches what's stored + charged. The end-date field stays directly editable for
an irregular span (the hotel checkout case), and editing it isn't overwritten by
the count effect. The count row shows the plan's unit ("× month").
Build+lint 12/12 (i18n parity).
Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V
julian
ff04ec10be