feat(aula-14): adicionar Istio Traffic Splitting com canary deployment

- Instala Istio (base + istiod + ingressgateway)
- Configura Kiali e Jaeger para observabilidade
- Deploy de app-backend v1 e v2 com traffic splitting 90/10
- Integra com Victoria Metrics da aula-12
- Inclui teste-stress.sh para validar distribuição de tráfego
- Tráfego externo passa pelo Istio Gateway via NGINX Ingress

aula-14/istio/kiali-values.yaml

@@ -0,0 +1,24 @@
+# Kiali - Service Mesh Observability
+# Dashboard para visualizar tráfego do Istio
+
+server:
+  web_root: /kiali
+
+auth:
+  strategy: anonymous
+
+deployment:
+  accessible_namespaces:
+    - "**"
+  ingress:
+    enabled: false
+
+external_services:
+  prometheus:
+    url: http://vmsingle-victoria-metrics-k8s-stack.monitoring:8429
+  tracing:
+    enabled: true
+    in_cluster_url: http://tracing.istio-system:16685/jaeger
+    use_grpc: true
+  grafana:
+    enabled: false