Initial commit: backend code

src/main/java/com/example/building/entity/StockFlow.java

@@ -0,0 +1,66 @@
+package com.example.building.entity;
+
+import com.baomidou.mybatisplus.annotation.*;
+import lombok.Data;
+
+import java.time.LocalDateTime;
+
+/**
+ * 库存流水实体类
+ * 记录库存变动历史
+ */
+@Data
+@TableName("stock_flow")
+public class StockFlow {
+
+    @TableId(type = IdType.ASSIGN_UUID)
+    private String flowId;
+
+    /**
+     * 商品ID
+     */
+    private String productId;
+
+    /**
+     * 类型: 1入库 2出库 3调整 4盘点
+     */
+    private Integer type;
+
+    /**
+     * 变动数量(正数增加/负数减少)
+     */
+    private Integer quantity;
+
+    /**
+     * 变动前数量
+     */
+    private Integer beforeQuantity;
+
+    /**
+     * 变动后数量
+     */
+    private Integer afterQuantity;
+
+    /**
+     * 关联单据ID
+     */
+    private String relatedId;
+
+    /**
+     * 关联单据类型
+     */
+    private String relatedType;
+
+    /**
+     * 操作人ID
+     */
+    private String operatorId;
+
+    /**
+     * 备注
+     */
+    private String remark;
+
+    @TableField(fill = FieldFill.INSERT)
+    private LocalDateTime createdAt;
+}