feat: 添加管线阶段可视化展示并改进任务日志

- 添加 PipelineStages 组件，用圆角矩形和箭头展示管线阶段
- 三色方案：已完成为浅绿、进行中为浅橙、未完成为灰色
- 任务列表中显示进度百分比和管线阶段
- 增强后端日志输出，添加任务启动、进度更新和管线完成日志
- 用于诊断任务卡在 running 状态的问题

frontend/src/components/TaskListPanel.tsx

@@ -3,6 +3,7 @@ import { useParams } from 'react-router-dom'
 import { getTasks } from '../api/project'
 import type { Task } from '../api/types'
 import StatusBadge from './StatusBadge'
+import PipelineStages from './PipelineStages'
 import Skeleton from './Skeleton'
 
 const ASSET_TYPE_LABELS: Record<string, string> = {
@@ -103,9 +104,17 @@ export default function TaskListPanel() {
               >
                 {task.prompt}
               </p>
-              <span style={{ fontSize: 11, color: 'var(--text-muted)', marginTop: 4, display: 'block' }}>
-                {formatRelativeTime(task.createdAt)}
-              </span>
+              <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', marginTop: 4 }}>
+                <span style={{ fontSize: 11, color: 'var(--text-muted)' }}>
+                  {formatRelativeTime(task.createdAt)}
+                </span>
+                {task.progress !== undefined && task.status === 'running' && (
+                  <span style={{ fontSize: 11, color: 'var(--text-muted)' }}>
+                    {task.progress}%
+                  </span>
+                )}
+              </div>
+              <PipelineStages currentStage={task.stage ?? null} status={task.status} />
             </a>
           ))
         )}