- 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>