feat(downloads): fold download plans into download panel (DL-3)

- Waiting plans (approval / disk space / automation off / queued) are
  active-segment rows on /download-tasks/board, merged by created_at,
  counted, with approve / cancel actions; ?plan= deep links and legacy
  /downloads/plans routes redirect to the panel
- Download detail shows "why this download" (source, purpose, replaced
  version, reasons); raw evaluation in tech info
- Failed / cancelled / expired plans appear in the entity download
  history; rejected / revoked / expired approvals close draft plans
- New GET /acquisition-plans/{id}/why, POST /acquisition-plans/{id}/cancel
- User-facing copy no longer says 下载计划; glossary updated

Co-Authored-By: Claude Opus 5.5 <[email protected]>

apps/web/app/routes/console/tasks.tsx

@@ -15,7 +15,7 @@ import { legacyRedirectLoader } from "./redirects.ts";
 
 export const meta = () => [{ title: "任务 · UHD 媒体自动化控制台" }];
 
-// 旧的 ?tab=downloads / plans / business / plan 跳到下载面板 / 下载计划 / 任务流 / 计划页
+// 旧的 ?tab=downloads / plans / business / plan 跳到下载面板 / 下载面板 / 任务流 / 计划页
 export const clientLoader = legacyRedirectLoader;
 
 type Tab = StreamTab;