Reach past cancellations too

Win-back campaigns used to email only customers who cancelled after the campaign was created. Past cancellations, the customers who already left before a shop ever set one up, were out of reach.

The all-reasons win-back campaign form now has an "Also send to customers who already cancelled" toggle with a window the merchant picks, plus a restart card on the pages that lead into it. Turning it on and saving enrols those past cancellations in the campaign; each one gets only the campaign's first email, never the full sequence a fresh cancellation would see.

The toggle is off by default on every campaign, so nothing changes until a merchant turns it on and saves. No feature flag or pilot gates it: every shop can see and use it now.

This is one more way to put an existing win-back campaign to work on a shop's full cancellation history, not just what happens from today onward.