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。

bun.lock

@@ -9,6 +9,14 @@
         "typescript": "^7.0.2",
       },
     },
+    "apps/engine": {
+      "name": "@new-api-key-usage/engine",
+      "version": "0.0.0",
+      "dependencies": {
+        "@new-api-key-usage/core": "workspace:*",
+        "@new-api-key-usage/db": "workspace:*",
+      },
+    },
     "apps/server": {
       "name": "@new-api-key-usage/server",
       "version": "0.0.0",
@@ -291,6 +299,8 @@
 
     "@new-api-key-usage/db": ["@new-api-key-usage/db@workspace:packages/db"],
 
+    "@new-api-key-usage/engine": ["@new-api-key-usage/engine@workspace:apps/engine"],
+
     "@new-api-key-usage/server": ["@new-api-key-usage/server@workspace:apps/server"],
 
     "@new-api-key-usage/web": ["@new-api-key-usage/web@workspace:apps/web"],