feat(ai-companion): 新增AI角色点赞功能

新增点赞/取消点赞接口，包含实体、Mapper、Service及DTO，支持用户点赞状态切换与异常处理。

src/main/java/com/yolo/keyborad/mapper/KeyboardAiCompanionLikeMapper.java

@@ -0,0 +1,12 @@
+package com.yolo.keyborad.mapper;
+
+import com.baomidou.mybatisplus.core.mapper.BaseMapper;
+import com.yolo.keyborad.model.entity.KeyboardAiCompanionLike;
+
+/*
+* @author: ziin
+* @date: 2026/1/27 18:18
+*/
+    
+public interface KeyboardAiCompanionLikeMapper extends BaseMapper<KeyboardAiCompanionLike> {
+}