feat(common): 新增多个 VO 类

- 新增了多个与公司、合同、项目、库存等相关的 VO 类
- 这些类用于数据传输和接口定义，提高了系统的可维护性和扩展性
- 使用了 Lombok 注解，简化了类的编写

common/src/main/java/com/ecep/contract/vo/PurchaseOrderItemVo.java

@@ -0,0 +1,22 @@
+package com.ecep.contract.vo;
+
+import com.ecep.contract.model.IdentityEntity;
+import lombok.Data;
+
+@Data
+public class PurchaseOrderItemVo implements IdentityEntity {
+    private Integer id;
+    private Integer purchaseOrderId;
+    private Integer contractItemId;
+    private Integer inventoryId;
+    private String itemName;
+    private Integer unitId;
+    private Double quantity;
+    private Double unitPrice;
+    private Double totalPrice;
+    private Double taxRate;
+    private Double taxAmount;
+    private Double totalAmount;
+    private Integer order;
+    private String remark;
+}