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/templates/deployment.yaml

@@ -0,0 +1,94 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: {{ include "parent-bff.name" . }}
+  namespace: {{ .Values.namespace }}
+  labels:
+    {{- include "parent-bff.labels" . | nindent 4 }}
+spec:
+  replicas: {{ .Values.replicaCount }}
+  selector:
+    matchLabels:
+      {{- include "parent-bff.selectorLabels" . | nindent 6 }}
+  strategy:
+    type: {{ .Values.strategy.type }}
+    rollingUpdate:
+      maxSurge: {{ .Values.strategy.maxSurge }}
+      maxUnavailable: {{ .Values.strategy.maxUnavailable }}
+  template:
+    metadata:
+      labels:
+        {{- include "parent-bff.selectorLabels" . | nindent 8 }}
+        app.kubernetes.io/part-of: edu-platform
+        app.kubernetes.io/component: bff
+      {{- if .Values.metrics.enabled }}
+      annotations:
+        prometheus.io/scrape: "true"
+        prometheus.io/port: {{ .Values.metrics.port | quote }}
+        prometheus.io/path: {{ .Values.metrics.path | quote }}
+      {{- end }}
+    spec:
+      {{- if .Values.podAntiAffinity.enabled }}
+      affinity:
+        podAntiAffinity:
+          preferredDuringSchedulingIgnoredDuringExecution:
+            - weight: 100
+              podAffinityTerm:
+                labelSelector:
+                  matchLabels:
+                    {{- include "parent-bff.selectorLabels" . | nindent 20 }}
+                topologyKey: {{ .Values.podAntiAffinity.topologyKey }}
+      {{- end }}
+      containers:
+        - name: {{ include "parent-bff.name" . }}
+          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
+          imagePullPolicy: {{ .Values.image.pullPolicy }}
+          ports:
+            - name: http
+              containerPort: {{ .Values.service.targetPort }}
+              protocol: TCP
+          livenessProbe:
+            httpGet:
+              path: {{ .Values.probes.liveness.path }}
+              port: http
+            initialDelaySeconds: {{ .Values.probes.liveness.initialDelaySeconds }}
+            periodSeconds: {{ .Values.probes.liveness.periodSeconds }}
+            timeoutSeconds: {{ .Values.probes.liveness.timeoutSeconds }}
+            failureThreshold: {{ .Values.probes.liveness.failureThreshold }}
+          readinessProbe:
+            httpGet:
+              path: {{ .Values.probes.readiness.path }}
+              port: http
+            initialDelaySeconds: {{ .Values.probes.readiness.initialDelaySeconds }}
+            periodSeconds: {{ .Values.probes.readiness.periodSeconds }}
+            timeoutSeconds: {{ .Values.probes.readiness.timeoutSeconds }}
+            failureThreshold: {{ .Values.probes.readiness.failureThreshold }}
+          resources:
+            {{- toYaml .Values.resources | nindent 12 }}
+          env:
+            {{- if .Values.configMap.enabled }}
+            {{- range $k, $v := .Values.configMap.data }}
+            - name: {{ $k }}
+              valueFrom:
+                configMapKeyRef:
+                  name: {{ include "parent-bff.name" $ }}-config
+                  key: {{ $k }}
+            {{- end }}
+            {{- end }}
+            {{- range $secret := .Values.secretRefs }}
+            {{- range $key := $secret.keys }}
+            - name: {{ $key }}
+              valueFrom:
+                secretKeyRef:
+                  name: {{ $secret.name }}
+                  key: {{ $key }}
+            {{- end }}
+            {{- end }}
+            {{- if .Values.kafka.enabled }}
+            - name: KAFKA_BROKERS
+              value: {{ .Values.kafka.brokers | quote }}
+            - name: KAFKA_CONSUMER_GROUP_ID
+              value: {{ .Values.kafka.consumerGroupId | quote }}
+            {{- end }}
+          securityContext:
+            {{- toYaml .Values.securityContext | nindent 12 }}