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/test/unit/lru.cache.test.ts

@@ -0,0 +1,99 @@
+import { describe, it, expect, beforeEach } from "vitest";
+import { LruCache } from "../../src/shared/cache/lru.cache.js";
+
+describe("LruCache", () => {
+  let cache: LruCache;
+
+  beforeEach(() => {
+    cache = new LruCache(3);
+  });
+
+  describe("set / get", () => {
+    it("应该存取值", () => {
+      cache.set("key1", "value1", 60);
+      expect(cache.get("key1")).toBe("value1");
+    });
+
+    it("未设置的 key 返回 null", () => {
+      expect(cache.get("nonexistent")).toBeNull();
+    });
+  });
+
+  describe("TTL 过期", () => {
+    it("过期后返回 null", async () => {
+      cache.set("key1", "value1", 0.01);
+      await new Promise((resolve) => setTimeout(resolve, 20));
+      expect(cache.get("key1")).toBeNull();
+    });
+
+    it("未过期时返回值", () => {
+      cache.set("key1", "value1", 60);
+      expect(cache.get("key1")).toBe("value1");
+    });
+  });
+
+  describe("LRU 淘汰", () => {
+    it("容量满时淘汰最久未使用的条目", () => {
+      cache.set("a", "1", 60);
+      cache.set("b", "2", 60);
+      cache.set("c", "3", 60);
+      cache.set("d", "4", 60);
+
+      expect(cache.get("a")).toBeNull();
+      expect(cache.get("b")).toBe("2");
+      expect(cache.get("c")).toBe("3");
+      expect(cache.get("d")).toBe("4");
+    });
+
+    it("访问后更新 LRU 顺序", () => {
+      cache.set("a", "1", 60);
+      cache.set("b", "2", 60);
+      cache.set("c", "3", 60);
+
+      cache.get("a");
+
+      cache.set("d", "4", 60);
+
+      expect(cache.get("a")).toBe("1");
+      expect(cache.get("b")).toBeNull();
+    });
+  });
+
+  describe("delete", () => {
+    it("删除后返回 null", () => {
+      cache.set("key1", "value1", 60);
+      cache.delete("key1");
+      expect(cache.get("key1")).toBeNull();
+    });
+  });
+
+  describe("clear", () => {
+    it("清空所有条目", () => {
+      cache.set("a", "1", 60);
+      cache.set("b", "2", 60);
+      cache.clear();
+      expect(cache.size).toBe(0);
+    });
+  });
+
+  describe("size", () => {
+    it("返回当前条目数", () => {
+      expect(cache.size).toBe(0);
+      cache.set("a", "1", 60);
+      expect(cache.size).toBe(1);
+      cache.set("b", "2", 60);
+      expect(cache.size).toBe(2);
+    });
+  });
+
+  it("默认 maxSize 为 100", () => {
+    const defaultCache = new LruCache();
+    for (let i = 0; i < 100; i++) {
+      defaultCache.set(`key${i}`, `val${i}`, 60);
+    }
+    expect(defaultCache.size).toBe(100);
+    defaultCache.set("key100", "val100", 60);
+    expect(defaultCache.size).toBe(100);
+    expect(defaultCache.get("key0")).toBeNull();
+  });
+});