feat: Implement pagination and effective account validation for backdoor user login

ruoyi-system/src/main/java/com/ruoyi/system/mapper/SysUserMapper.java

@@ -23,6 +23,14 @@ public interface SysUserMapper
      */
     List<SysUser> selectBackDoorUserList(@Param("keyword") String keyword, @Param("limit") int limit);
 
+    /**
+     * 查询指定账号在后门登录规则下的最新有效用户 ID。
+     *
+     * @param userName 用户账号
+     * @return 最新未删除记录的用户 ID
+     */
+    Long selectBackDoorEffectiveUserId(@Param("userName") String userName);
+
     /**
      * 根据条件分页查询用户列表
      * 

ruoyi-system/src/main/resources/mapper/system/SysUserMapper.xml

@@ -75,12 +75,20 @@ PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
                u.app_user_id,
                u.lc_userid,
                d.dept_name
-        from sys_user u
+        from (
+            select source_user.*,
+                   row_number() over (
+                       partition by source_user.user_name
+                       order by source_user.create_time desc nulls last, source_user.user_id desc
+                   ) as account_rank
+            from sys_user source_user
+            where source_user.del_flag = '0'
+              and source_user.user_name is not null
+              and source_user.user_name != ''
+        ) u
         left join sys_dept d on d.dept_id = u.dept_id
-        where u.del_flag = '0'
+        where u.account_rank = 1
           and u.status = '0'
-          and u.user_name is not null
-          and u.user_name != ''
         <if test="keyword != null and keyword != ''">
           and (
               cast(u.user_id as varchar) like concat('%', cast(#{keyword} as varchar), '%')
@@ -93,6 +101,15 @@ PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
                  u.user_id desc
         limit #{limit}
     </select>
+
+    <select id="selectBackDoorEffectiveUserId" resultType="java.lang.Long">
+        select u.user_id
+        from sys_user u
+        where u.del_flag = '0'
+          and u.user_name = #{userName}
+        order by u.create_time desc nulls last, u.user_id desc
+        limit 1
+    </select>
 	
 	<sql id="selectUserVo">
         select u.user_id, u.dept_id, u.user_name, u.nick_name, u.email, u.avatar, u.phonenumber, u.password, u.sex, u.status, u.del_flag, u.login_ip, u.login_date, u.create_by, u.create_time, u.remark,