Phase 5: Outbox DLQ, Monitoring, Consumer-Registry

- Migration 0092: DLQ columns (error_message, failed_at) + consumer_inbox RLS fix
- outbox.py: DLQ logic, replay functions, stats, consumer registry
- app/routes/outbox.py: 5 API endpoints (stats, failed, replay, replay-all, consumer-registry)
- outbox_deliveries tracking per consumer handler
- 18/18 tests passing

app/models/__init__.py

@@ -13,6 +13,7 @@ from app.models.contact_merge import ContactMergeHistory
 from app.models.entity_permission import EntityPermission
 from app.models.guest_user import GuestUser
 from app.models.consumer_inbox import ConsumerInbox
+from app.models.outbox_delivery import OutboxDelivery
 from app.models.guest_invitation import GuestInvitation
 from app.models.entity_policy import EntityPolicy
 from app.models.permission_template import PermissionTemplate