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/components/console/nav.ts

@@ -90,7 +90,7 @@ export const NAV_GROUPS: NavGroup[] = [
   {
     title: "整理",
     items: [
-      { to: "/console/downloads", label: "下载面板", icon: Download, description: "下载任务、下载计划与下载盘" },
+      { to: "/console/downloads", label: "下载面板", icon: Download, description: "进行中与已完成的下载、下载盘" },
       {
         to: "/console/organize",
         label: "整理记录",