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/app-backend/v1/Dockerfile

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+FROM node:24-alpine
+WORKDIR /app
+COPY app.js .
+EXPOSE 3000
+USER node
+CMD ["node", "app.js"]

aula-14/app-backend/v1/app.js

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+const http = require("http");
+
+const MAX_REQUESTS = parseInt(process.env.MAX_REQUESTS) || 5;
+let requestCount = 0;
+let frozen = false;
+
+const server = http.createServer((req, res) => {
+  if (frozen) {
+    return;
+  }
+
+  requestCount++;
+  console.log(`[v1] request ${requestCount}/${MAX_REQUESTS}`);
+
+  if (requestCount >= MAX_REQUESTS) {
+    frozen = true;
+    console.log("[v1] Aplicação travou");
+  }
+
+  if (req.url === "/health") {
+    res.writeHead(200);
+    res.end("ok");
+    return;
+  }
+
+  res.writeHead(200);
+  res.end(`v1 - Request ${requestCount}\n`);
+});
+
+server.listen(3000, () => {
+  console.log(`[v1] Porta 3000 (trava após ${MAX_REQUESTS} requests)`);
+});

aula-14/app-backend/v2/Dockerfile

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+FROM node:24-alpine
+WORKDIR /app
+COPY app.js .
+EXPOSE 3000
+USER node
+CMD ["node", "app.js"]

aula-14/app-backend/v2/app.js

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+const http = require("http");
+
+let requestCount = 0;
+
+const server = http.createServer((req, res) => {
+  if (req.url === "/health") {
+    res.writeHead(200);
+    res.end("ok");
+    return;
+  }
+
+  requestCount++;
+  console.log(`[v2] request ${requestCount}`);
+
+  res.writeHead(200);
+  res.end(`v2 - Request ${requestCount}\n`);
+});
+
+server.listen(3000, () => {
+  console.log("[v2] Porta 3000 (estável)");
+});