fix: serialize phase4 inventory and outbound gates

lastleg-service/src/main/java/com/baiyue/lastleg/service/LoadingCompletedConsumer.java

@@ -17,6 +17,7 @@ import jakarta.annotation.Resource;
 import org.springframework.dao.DuplicateKeyException;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
+import org.springframework.transaction.annotation.Isolation;
 import com.baomidou.mybatisplus.core.toolkit.IdWorker;
 import java.math.BigDecimal;
 import java.time.LocalDateTime;
@@ -41,7 +42,7 @@ public class LoadingCompletedConsumer {
     @Resource private DropshipOrderService dropshipOrders;
     @Resource private InventoryCommandService inventory;
 
-    @Transactional
+    @Transactional(isolation = Isolation.READ_COMMITTED)
     public int consume(EventEnvelope envelope) {
         envelope.requireValid();
         if (!EventTypes.FIRST_LEG_LOADING_PLAN_COMPLETED.equals(envelope.eventType())