fix: update letzshop API to use unified Order model properties

- Change message exceptions (MessageAttachmentException,
  InvalidConversationTypeException, InvalidRecipientTypeException)
  to extend BusinessLogicException instead of ValidationException
  which doesn't accept error_code parameter

- Update vendor letzshop API endpoints:
  - Change sync_status query param to status in list_orders()
  - Fix response mapping to use unified Order model properties
    (external_order_id, external_shipment_id, status, etc.)
  - Fix confirm_order() to get inventory unit IDs from order items
  - Fix set_tracking() to use external_shipment_id

- Add order_date to test fixtures (required NOT NULL field)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/integration/api/v1/admin/test_letzshop.py

@@ -246,6 +246,8 @@ class TestAdminLetzshopOrdersAPI:
 
     def test_list_vendor_orders_with_data(self, client, db, admin_headers, test_vendor):
         """Test listing vendor orders with data."""
+        from datetime import datetime, timezone
+
         from models.database.order import Order
 
         # Create test order using unified Order model with all required fields
@@ -256,6 +258,7 @@ class TestAdminLetzshopOrdersAPI:
             channel="letzshop",
             external_order_id="admin_order_1",
             status="pending",
+            order_date=datetime.now(timezone.utc),
             customer_first_name="Admin",
             customer_last_name="Test",
             customer_email="admin-test@example.com",