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

infra/k8s/helm/parent-bff/values-prod.yaml

@@ -0,0 +1,35 @@
+# parent-bff 生产环境
+
+replicaCount: 3
+
+image:
+  tag: prod
+
+configMap:
+  data:
+    NODE_ENV: production
+    LOG_LEVEL: info
+    DEV_MODE: "false"
+    CORS_ORIGINS: https://parent.edu.example.com
+
+resources:
+  requests:
+    cpu: 500m
+    memory: 512Mi
+  limits:
+    cpu: 2000m
+    memory: 2Gi
+
+hpa:
+  enabled: true
+  minReplicas: 3
+  maxReplicas: 10
+  targetCPUUtilizationPercentage: 70
+  targetMemoryUtilizationPercentage: 80
+
+podAntiAffinity:
+  enabled: true
+
+kafka:
+  enabled: true
+  brokers: kafka.edu-system.svc.cluster.local:9092