feat(tenant-balance): 新增查询自身及下级余额接口

- Controller 增加 /get-self-amount 与 /get-self-subordinate-amount-page 端点
- Service 与 Mapper 实现当前租户余额查询及下级分页查询
- RespVO 移除乐观锁字段，改用 updatedAt 并补充 tenantName 展示

yudao-module-system/src/main/resources/mapper/TenantBalanceMapper.xml

@@ -21,4 +21,17 @@
         </where>
             order by stb.id desc
     </select>
+
+    <select id="selectPageWithSelfSubordinateTenant"
+            resultType="cn.iocoder.yudao.module.system.controller.admin.tenantbalance.vo.TenantBalanceRespVO">
+        select stb.*, st.name as tenantName from system_tenant_balance as stb
+        left join system_tenant as st on stb.id = st.id
+        <where>
+            and st.parent_Id = #{tenantId,jdbcType=BIGINT}
+            <if test="pageReqVO.id != null">
+                and stb.id = #{pageReqVO.id,jdbcType=BIGINT}
+            </if>
+        </where>
+        order by stb.id desc
+    </select>
 </mapper>