Send cancellation notice as ticket comment to customer

Cancellation webhooks don't create a public ticket message, leaving customers unsure about equipment return and billing. Provide a public ticket comment so returns complete before the next billing run.

Overview

Cancellation events that never create a public ticket comment leave returns and billing unresolved. This flow publishes a templated, customer-facing comment so customers get clear return instructions within minutes and support and billing share a single record ahead of the next billing run.