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/k8s/ingress-app.yaml

@@ -0,0 +1,23 @@
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: app-backend
+  namespace: istio-system
+  annotations:
+    nginx.ingress.kubernetes.io/backend-protocol: HTTP
+    nginx.ingress.kubernetes.io/upstream-vhost: "${APP_HOST}"
+    ${TLS_ANNOTATION}
+spec:
+  ingressClassName: nginx
+  ${TLS_CONFIG}
+  rules:
+    - host: ${APP_HOST}
+      http:
+        paths:
+          - path: /
+            pathType: Prefix
+            backend:
+              service:
+                name: istio-ingressgateway
+                port:
+                  number: 80