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/PipelineStages.tsx

@@ -0,0 +1,71 @@
+const STAGES = [
+  { key: 'prompt_builder', label: '提示词' },
+  { key: 'asset_generator', label: '生成中' },
+  { key: 'quality_supervisor', label: '质检中' },
+  { key: 'format_adapter', label: '格式转换' },
+] as const
+
+type Stage = typeof STAGES[number]['key']
+
+interface PipelineStagesProps {
+  currentStage: Stage | null
+  status: string
+}
+
+export default function PipelineStages({ currentStage, status }: PipelineStagesProps) {
+  if (!currentStage || status !== 'running') {
+    return null
+  }
+
+  const currentIndex = STAGES.findIndex(s => s.key === currentStage)
+
+  return (
+    <div style={{ marginTop: 8, display: 'flex', alignItems: 'center', gap: 4 }}>
+      {STAGES.map((stage, index) => {
+        let bgColor: string
+        let textColor: string
+
+        if (index < currentIndex) {
+          bgColor = 'rgba(74, 222, 128, 0.15)'
+          textColor = '#4ade80'
+        } else if (index === currentIndex) {
+          bgColor = 'rgba(251, 146, 60, 0.15)'
+          textColor = '#fb923c'
+        } else {
+          bgColor = 'rgba(156, 163, 175, 0.1)'
+          textColor = '#9ca3af'
+        }
+
+        return (
+          <div key={stage.key} style={{ display: 'flex', alignItems: 'center' }}>
+            <span
+              style={{
+                padding: '4px 8px',
+                borderRadius: 6,
+                fontSize: 11,
+                fontWeight: 500,
+                backgroundColor: bgColor,
+                color: textColor,
+                whiteSpace: 'nowrap',
+              }}
+            >
+              {stage.label}
+            </span>
+            {index < STAGES.length - 1 && (
+              <span
+                style={{
+                  marginLeft: 4,
+                  marginRight: 4,
+                  fontSize: 12,
+                  color: '#9ca3af',
+                }}
+              >
+                →
+              </span>
+            )}
+          </div>
+        )
+      })}
+    </div>
+  )
+}

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>
           ))
         )}