feat: initialize parent-bff service with full core features

add complete parent-bff implementation including:
- GraphQL endpoint with depth/cost validation
- ChildGuard越权校验 with redis cache and singleflight
- parallel orchestration with partial failure fallback
- three-level cache fallback strategy (Redis + LRU + downstream)
- Kafka consumer for cache invalidation and notification push
- opossum circuit breaker for downstream services
- Prometheus metrics and SLO alerts
- Helm chart for k8s deployment with multi-environment configs
- Grafana dashboard for observability
- complete unit and integration tests

services/parent-bff/src/main.ts

@@ -0,0 +1,62 @@
+import "reflect-metadata";
+import { NestFactory } from "@nestjs/core";
+import { AppModule } from "./app.module.js";
+import { GlobalErrorFilter } from "./shared/errors/global-error.filter.js";
+import { initTracer, shutdownTracer } from "./shared/observability/tracer.js";
+import { logger } from "./shared/observability/logger.js";
+import { env } from "./config/env.js";
+import { metricsRegistry } from "./shared/observability/metrics.js";
+import { closeRedisClient } from "./shared/cache/redis.client.js";
+import type { Request, Response } from "express";
+
+/**
+ * parent-bff 启动入口（对齐 02-architecture-design.md §6.7 优雅关闭）。
+ *
+ * 启动顺序：
+ * 1. initTracer（OTel SDK，可选，未配置 endpoint 时跳过）
+ * 2. NestFactory.create + GlobalErrorFilter
+ * 3. /metrics 端点（Prometheus 抓取）
+ * 4. app.listen(3010)
+ *
+ * SIGTERM 关闭顺序（P4.1 基础版，P5+ 补充 Kafka consumer）：
+ * 1. app.close()（拒绝新请求 + 等待 in-flight）
+ * 2. shutdownTracer()（flush OTel span）
+ * 3. process.exit(0)（由 NestJS enableShutdownHooks 触发）
+ */
+async function bootstrap(): Promise<void> {
+  initTracer();
+
+  const app = await NestFactory.create(AppModule, {
+    logger: ["log", "error", "warn"],
+  });
+
+  app.useGlobalFilters(new GlobalErrorFilter());
+  app.enableShutdownHooks();
+
+  // Prometheus 指标端点：不鉴权，供 Prometheus 抓取。
+  app.getHttpAdapter().get("/metrics", async (_req: Request, res: Response) => {
+    res.set("Content-Type", metricsRegistry.contentType);
+    res.end(await metricsRegistry.metrics());
+  });
+
+  // CORS：默认允许 parent-portal（localhost:4002）
+  app.enableCors({
+    origin: env.CORS_ORIGINS.split(",").map((o) => o.trim()),
+    credentials: true,
+  });
+
+  await app.listen(env.PORT);
+  logger.info({ port: env.PORT, devMode: env.DEV_MODE }, "Parent BFF started");
+
+  process.on("SIGTERM", async () => {
+    logger.info("Parent BFF received SIGTERM, shutting down...");
+    await app.close();
+    await closeRedisClient();
+    await shutdownTracer();
+  });
+}
+
+bootstrap().catch((err: unknown) => {
+  logger.error({ err }, "Failed to start Parent BFF");
+  process.exit(1);
+});