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/engine/src/env.ts

@@ -0,0 +1,43 @@
+export interface EngineEnv {
+  DATABASE_URL: string;
+  SK_KEY_ENCRYPTION_SECRET: string;
+  NEWAPI_BASE: string;
+  SYNC_INTERVAL_MS: number;
+  LOG_LEVEL: "debug" | "info" | "warning" | "error" | "fatal";
+}
+
+function parseLogLevel(
+  value: string | undefined,
+): "debug" | "info" | "warning" | "error" | "fatal" {
+  const v = (value ?? "info").trim().toLowerCase();
+  if (
+    v === "debug" ||
+    v === "info" ||
+    v === "warning" ||
+    v === "error" ||
+    v === "fatal"
+  ) {
+    return v;
+  }
+  throw new Error("LOG_LEVEL must be debug|info|warning|error|fatal");
+}
+
+export function loadEnv(source: Record<string, string | undefined>): EngineEnv {
+  const databaseUrl = source.DATABASE_URL;
+  const secret = source.SK_KEY_ENCRYPTION_SECRET;
+  if (!databaseUrl) throw new Error("DATABASE_URL is required");
+  if (!secret) throw new Error("SK_KEY_ENCRYPTION_SECRET is required");
+
+  const interval = Number(source.SYNC_INTERVAL_MS ?? 300_000);
+  if (!Number.isInteger(interval) || interval < 1000) {
+    throw new Error("SYNC_INTERVAL_MS must be an integer >= 1000");
+  }
+
+  return {
+    DATABASE_URL: databaseUrl,
+    SK_KEY_ENCRYPTION_SECRET: secret,
+    NEWAPI_BASE: source.NEWAPI_BASE ?? "http://127.0.0.1:8080",
+    SYNC_INTERVAL_MS: interval,
+    LOG_LEVEL: parseLogLevel(source.LOG_LEVEL),
+  };
+}