Add opt-out summary and draft email to task

Investor opt-outs arrive as webhooks without a readable summary, so admin triage stalls. Coordinators receive a concise summary and draft email on the task so they can reply the same day.

Overview

Raw opt-out webhooks leave admin teams parsing payloads and drafting replies manually, which slows investor-facing response and record hygiene. This flow converts those payloads into a clear change summary and an editable email draft on the task, so coordinators can reply the same day and keep task records current.