Phase 107 complete:
- New table automation_email_once_deliveries with UNIQUE KEY (rule_id, action_id, order_id)
- AutomationEmailOnceRepository: wasSent() / markSent() with ON DUPLICATE KEY guard
- AutomationService: send_once_per_order flag — mark only on successful send
- Checkbox "Wyslij tylko raz dla tego zamowienia" in rule form (edit + new action JS)
- 2 unit tests added; 3/3 passing (49 assertions)
Milestone v3.1 Operational Enhancements: COMPLETE (2/2 phases)
Co-Authored-By: Claude <noreply@anthropic.com>
