chore: scaffold monorepo and migrate uhd_web design system (W0-A)

- pnpm workspace: apps/{web,server}, packages/{contracts,db,domain,adapters,tasks,agent,testkit}
- server: Hono + zod-openapi, API Key auth with scopes, redacting pino logger, SSE event bus with replay, worker heartbeat
- db: Kysely + pg, file migrator, 0001_init (settings/api_key/audit_event/outbox_event)
- web: React Router 7 SPA console shell with 12 workspace placeholders, uhd_web tokens/ui/guard scripts
- docs: ADR-001 (Node over Deno), dev runbook, design system rules

Co-Authored-By: Claude Fable 5.1 <[email protected]>

apps/web/app/components/prism-leak.tsx

@@ -0,0 +1,10 @@
+import { cn } from "~/lib/utils";
+
+/**
+ * 全站背景上左上角那束淡淡的棱镜漏光(样式见 app.css 的 .prism-leak)。
+ * 各页面外壳各放一个:用户中心、流媒体浏览页、公共页(落地页除外)、测速、404、退订。
+ * 放在背景层之后、内容之前;宿主是层叠上下文时用 -z-10 垫在内容下面。
+ */
+export default function PrismLeak({ className }: { className?: string }) {
+  return <div aria-hidden className={cn("prism-leak", className)} />;
+}