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/server/src/http/errors.ts

@@ -0,0 +1,15 @@
+import { API_ERROR_STATUS, type ApiErrorCode } from "@umt/contracts";
+
+/** 业务可抛出的 API 错误,由 app.onError 统一转换为信封 */
+export class ApiException extends Error {
+  readonly status: number;
+  constructor(
+    readonly code: ApiErrorCode,
+    message: string,
+  ) {
+    super(message);
+    this.status = API_ERROR_STATUS[code];
+  }
+}
+
+export const errorBody = (code: ApiErrorCode, message: string) => ({ ok: false as const, error: { code, message } });