- Add PATCH method to /api/designs/[id]/route.ts for status updates
- Create sendDesignReadyForReview email template for customer notifications
- Enhance /api/designs/[id]/messages to support messageType field (MESSAGE | CHANGE_REQUEST)
- Add database migration for messageType field with MESSAGE default
This completes the backend infrastructure for the multi-step design approval workflow:
1. Admin edits and sends design to customer for review
2. Customer approves design or requests changes
3. Admin receives notifications for change requests
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
