feat: 新增取消任务

src/main/java/com/goeing/printserver/main/PrintController.java

@@ -123,6 +123,35 @@ public class PrintController implements PrintService {
         return result;
     }
     
+    /**
+     * 取消单个任务
+     * 
+     * @param taskId 任务ID
+     * @return 取消结果
+     */
+    @DeleteMapping("queue/task/{taskId}")
+    public Map<String, Object> cancelTask(@PathVariable String taskId) {
+        Map<String, Object> result = new HashMap<>();
+        try {
+            boolean cancelled = printQueueService.cancelTask(taskId);
+            if (cancelled) {
+                result.put("success", true);
+                result.put("message", "任务已取消");
+                result.put("taskId", taskId);
+            } else {
+                result.put("success", false);
+                result.put("message", "未找到指定任务");
+                result.put("taskId", taskId);
+            }
+        } catch (Exception e) {
+            result.put("success", false);
+            result.put("message", "取消任务失败: " + e.getMessage());
+            result.put("taskId", taskId);
+        }
+        result.put("timestamp", System.currentTimeMillis());
+        return result;
+    }
+    
     /**
      * 搜索打印任务
      * 

src/main/java/com/goeing/printserver/main/service/PrintQueueService.java

@@ -383,6 +383,30 @@ public class PrintQueueService {
         return clearedCount;
     }
     
+    /**
+     * 取消指定任务
+     * @param taskId 任务ID
+     * @return 是否成功取消
+     */
+    public boolean cancelTask(String taskId) {
+        // 检查当前任务
+        if (currentTask != null && taskId.equals(currentTask.getId())) {
+            log.info("取消当前正在执行的任务: {}", taskId);
+            currentTask.setStatus("cancelled");
+            currentTask = null;
+            return true;
+        }
+        
+        // 从队列中移除任务
+        boolean removed = printQueue.removeIf(task -> taskId.equals(task.getId()));
+        if (removed) {
+            log.info("成功从队列中取消任务: {}", taskId);
+        } else {
+            log.warn("未找到要取消的任务: {}", taskId);
+        }
+        return removed;
+    }
+    
     /**
      * 获取历史服务实例
      *