fix: 修复排队状态查询逻辑

当任务没有 receiver_dept_id 时，从 task_unlock_status 表中查询对应的部门ID

backend/src/main/java/com/designhub/service/TaskItemService.java

@@ -187,14 +187,27 @@ public class TaskItemService {
             // 确定目标部门
             Long targetDeptId = deptId;
             if (targetDeptId == null) {
+                // 优先使用已接单的部门
                 targetDeptId = item.getReceiverDeptId();
             }
             
+            if (targetDeptId == null) {
+                // 🔥 从 task_unlock_status 表中查询该任务对应的部门
+                com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper<com.designhub.entity.TaskUnlockStatus> wrapper = 
+                    new com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper<>();
+                wrapper.eq(com.designhub.entity.TaskUnlockStatus::getTaskItemId, item.getId())
+                       .last("LIMIT 1");
+                com.designhub.entity.TaskUnlockStatus unlockStatus = taskUnlockService.getUnlockStatusMapper().selectOne(wrapper);
+                if (unlockStatus != null) {
+                    targetDeptId = unlockStatus.getDeptId();
+                }
+            }
+            
             // 填充解锁状态
             if (targetDeptId != null) {
                 taskUnlockService.fillUnlockStatus(item, targetDeptId, releaseType);
             } else {
-                // 无法确定部门，默认可抢
+                // 无法确定部门，默认可抢（兼容旧数据）
                 item.setUnlockStatus("unlocked");
                 item.setCanGrab(true);
             }

backend/src/main/java/com/designhub/service/TaskUnlockService.java

@@ -46,6 +46,13 @@ public class TaskUnlockService {
     private static final int DEFAULT_DAILY_UNLOCK_MIN = 5;
     private static final int DEFAULT_BATCH_SIZE = 5;
 
+    /**
+     * 获取 TaskUnlockStatusMapper（供其他 Service 使用）
+     */
+    public TaskUnlockStatusMapper getUnlockStatusMapper() {
+        return unlockStatusMapper;
+    }
+
     // ==================== 配置相关 ====================
 
     /**