feat(engine): 实现同步引擎与 engine_status 快照

apps/engine 独立进程（syncRound + 防重叠调度）；上游 log/token；QPU 采样；
server 读 engine_status；时刻出参 toUnixSec；中文日志；zod-openapi 扩展顺序修复。

apps/server/src/routes/admin-audit.ts

@@ -1,5 +1,5 @@
 import { OpenAPIHono, createRoute } from "@hono/zod-openapi";
-import { unixToIso, type AuditLogItem } from "@new-api-key-usage/core";
+import { toUnixSec, type AuditLogItem } from "@new-api-key-usage/core";
 import {
   requireAdminSession,
   type AppVars,
@@ -56,7 +56,7 @@ export function adminAuditRoutes() {
       });
       const items: AuditLogItem[] = rows.map((row) => ({
         id: row.id,
-        created_at: unixToIso(row.created_at)!,
+        created_at: toUnixSec(row.created_at)!,
         operator: row.operator,
         domain: row.domain as AuditLogItem["domain"],
         action: row.action,