Add canceled subscribers to churn segment for re-engagement

Canceled subscription notices don't reach retention lists, so coordinators miss context and outreach is delayed. Add them to a churn segment so coordinators can launch win-back emails within minutes.

Overview

When cancellations arrive without being routed to retention lists, coordinators lack context and outreach is delayed. This flow captures those cancellations and adds them to a churn segment automatically, enabling win-back emails to be sent within minutes.