feat(oa): 添加 AI 消息展示类型字段

- 在 SysOaAiMessage、SysOaAiMessageBo、SysOaAiMessageVo 中添加 renderType 字段
- 在 SysOaAiMessageMapper.xml 中更新映射配置- 用于支持 AI 消息的多种展示类型，如文本、图片等

ruoyi-oa/src/main/resources/mapper/oa/SysOaAiMessageMapper.xml

@@ -9,6 +9,7 @@ PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
         <result property="conversationId" column="conversation_id"/>
         <result property="role" column="role"/>
         <result property="content" column="content"/>
+        <result property="renderType" column="render_type"/>
         <result property="tokens" column="tokens"/>
         <result property="cost" column="cost"/>
         <result property="messageOrder" column="message_order"/>
@@ -17,7 +18,7 @@ PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
     </resultMap>
 
     <sql id="selectSysOaAiMessageVo">
-        select message_id, conversation_id, role, content, tokens, cost, message_order, create_time, create_by
+        select message_id, conversation_id, role, content, render_type, tokens, cost, message_order, create_time, create_by
         from sys_oa_ai_message
     </sql>