feat(system): 实现注册码功能并优化用户注册流程

- 新增注册码生成和验证功能- 实现系统设置管理，包括注册功能开关
- 更新前端界面，增加系统管理和注册码相关功能
- 修改数据库结构，添加系统设置和注册码表

biji-houdaun/src/main/java/com/test/bijihoudaun/mapper/RegistrationCodeMapper.java

@@ -0,0 +1,9 @@
+package com.test.bijihoudaun.mapper;
+
+import com.baomidou.mybatisplus.core.mapper.BaseMapper;
+import com.test.bijihoudaun.entity.RegistrationCode;
+import org.apache.ibatis.annotations.Mapper;
+
+@Mapper
+public interface RegistrationCodeMapper extends BaseMapper<RegistrationCode> {
+}

biji-houdaun/src/main/java/com/test/bijihoudaun/mapper/SystemSettingMapper.java

@@ -0,0 +1,9 @@
+package com.test.bijihoudaun.mapper;
+
+import com.baomidou.mybatisplus.core.mapper.BaseMapper;
+import com.test.bijihoudaun.entity.SystemSetting;
+import org.apache.ibatis.annotations.Mapper;
+
+@Mapper
+public interface SystemSettingMapper extends BaseMapper<SystemSetting> {
+}