feat(entity): 新增 Deliveries 和 Items 实体类

- 创建 Deliveries 类，包含配送相关的属性- 创建 Items 类，包含商品相关的属性
- 使用 Lombok 注解简化实体类代码

trading_platform/src/main/java/com/trading_platform/entity/Deliveries.java

@@ -0,0 +1,12 @@
+package com.trading_platform.entity;
+
+import lombok.Data;
+
+@Data
+public class Deliveries {
+    private int delivery_id;
+    private int order_id;
+    private int delivery_person_id;
+    private String  delivery_status ;
+    private String delivery_at;
+}

trading_platform/src/main/java/com/trading_platform/entity/Items.java

@@ -0,0 +1,16 @@
+package com.trading_platform.entity;
+
+import lombok.Data;
+
+@Data
+public class Items {
+    private int item_id;
+    private int user_id;
+    private String item_name;
+    private String description;
+    private int category_id;
+    private double price;
+    private String status;
+    private String create_at;
+    private String update_at;
+}