feat: add backdoor login functionality for testing environment

- Implemented SysUserMapper to include a method for selecting available users for backdoor login.
- Created XML mappings for the new backdoor user selection query.
- Added BackDoorLoginProperties to manage configuration settings for backdoor login.
- Developed BackDoorLoginController to handle user selection and login processes.
- Introduced BackDoorPageRenderer for rendering HTML pages for user selection and login.
- Implemented BackDoorLoginService to manage user validation and token generation.
- Added HTML templates for user selection, login, and error handling.
- Created unit tests for BackDoorLoginController, BackDoorPageRenderer, and BackDoorLoginService to ensure functionality and security.
- Documented usage and configuration in test-backdoor-login.md.

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

@@ -14,6 +14,15 @@ import com.ruoyi.common.core.domain.entity.SysUser;
  */
 public interface SysUserMapper
 {
+    /**
+     * 查询测试环境后门登录页可选择的正常 PC 用户。
+     *
+     * @param keyword 用户 ID、账号、姓名或手机号关键字
+     * @param limit 最大返回数量
+     * @return 可登录用户
+     */
+    List<SysUser> selectBackDoorUserList(@Param("keyword") String keyword, @Param("limit") int limit);
+
     /**
      * 根据条件分页查询用户列表
      *