feat: add week 3 audio and timeline enhancements

README.md

@@ -135,6 +135,8 @@ npm run build
 | GET | `/api/generations/{story_id}/jobs` | 查询故事生成与重试历史 |
 | GET | `/api/generations/{story_id}/provider-stats` | 查询 Provider 调用聚合指标 |
 | GET | `/api/generations/provider-analytics` | 查询当前用户跨故事 Provider 运营摘要 |
+| GET | `/api/audio/{story_id}/status` | 查询音频缓存状态，不触发生成 |
+| DELETE | `/api/audio/{story_id}/cache` | 清理故事音频缓存 |
 | GET | `/api/stories` | 故事列表 |
 | GET | `/api/stories/{story_id}` | 故事详情 |
 | DELETE | `/api/stories/{story_id}` | 删除故事 |
@@ -147,6 +149,7 @@ npm run build
 - `docs/product/unified-generation-workflow-prd.md`：统一生成工作流 PRD
 - `docs/planning/week-1-execution-backlog.md`：短期执行 backlog
 - `docs/planning/week-2-execution-backlog.md`：下一阶段执行 backlog
+- `docs/planning/week-2-to-4-execution-backlog.md`：Week 2 到 Week 4 总执行 backlog
 - `docs/planning/demo-checklist.md`：求职演示检查清单
 - `docs/planning/demo-validation-log.md`：本地 Docker 演示验证记录
 - `docs/planning/interview-pitch.md`：3 分钟项目讲解稿