fix: 修复Customer重复字段和OrderController错误导入

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

@@ -66,11 +66,6 @@ public class Customer {
      */
     private LocalDateTime lastLoginAt;
 
-    /**
-     * 最后登录时间（用于订单客户排序）
-     */
-    private LocalDateTime lastLoginAt;
-
     @TableField(fill = FieldFill.INSERT)
     private LocalDateTime createdAt;