feat(printer): 实现任务状态的原子性更新与同步锁机制

- 添加 compareAndSetTaskStatus 方法以支持基于期望状态的任务更新
- 引入 ReentrantLock 实现任务同步处理，防止并发冲突
- 在 XML 映射文件中定义 compareAndSetTaskStatus 的 SQL 更新语句
- 定义任务状态常量：TASK_STATUS_PENDING 和 TASK_STATUS_PROCESSING
- 优化任务获取逻辑，确保任务状态在处理前正确更新为 PROCESSING

src/main/resources/mapper/PrinterMapper.xml

@@ -152,6 +152,11 @@
     <update id="updateTaskStatus">
         UPDATE print_task SET status = #{status}, update_time = NOW() WHERE id = #{id}
     </update>
+    <update id="compareAndSetTaskStatus">
+        UPDATE print_task
+        SET status = #{newStatus}, update_time = NOW()
+        WHERE id = #{id} AND status = #{expectStatus}
+    </update>
     <update id="setPhotoCropped">
         UPDATE member_print SET crop_url = #{url}, update_time = NOW(), print_url = null WHERE id = #{id}
     </update>
@@ -172,4 +177,4 @@
     <delete id="deleteUserPhoto">
         DELETE FROM member_print WHERE member_id = #{memberId} AND scenic_id = #{scenicId} AND id = #{relationId} LIMIT 1;
     </delete>
-</mapper>
+</mapper>