Revert "fix: add db.rollback() to prevent session state corruption during historical import"

This reverts commit fadc9036a2.

app/services/letzshop/order_service.py

@@ -711,10 +711,6 @@ class LetzshopOrderService:
                     self.create_order(vendor_id, shipment)
                     stats["imported"] += 1
                 except Exception as e:
-                    # Rollback session to clear any partial changes from failed order
-                    # This is crucial because create_letzshop_order may have flushed
-                    # the order before the exception was raised (e.g., product not found)
-                    self.db.rollback()
                     stats["errors"] += 1
                     stats["error_messages"].append(
                         f"Shipment {shipment_id}: {str(e)}"