aula-15: implementação completa APM (Tempo + OTel + demo app)

Componentes:
- tempo-values.yaml: Grafana Tempo monolithic, 256Mi, 10Gi PVC
- otel-collector-values.yaml: recebe OTLP, exporta traces→Tempo,
  gera span metrics (RED)→Victoria Metrics via spanmetrics connector
- demo-app/: Node.js com rotas /fast (1 query), /slow (N+1, 51 queries),
  /fixed (JOIN), auto-instrumentado com OpenTelemetry
- alerts/latency-alerts.yaml: VMRule com Doherty threshold (p95>400ms)
- setup.sh: instala Tempo, OTel Collector, configura Grafana datasource,
  deploy demo app via ConfigMap (sem Docker build necessário)
- cleanup.sh: remove apenas recursos da aula-15, preserva aula-12

Zero hardcoded hostnames. Tudo via .env e placeholders.

aula-15/demo-app/tracing.js

@@ -0,0 +1,45 @@
+'use strict';
+
+const { NodeSDK } = require('@opentelemetry/sdk-node');
+const { getNodeAutoInstrumentations } = require('@opentelemetry/auto-instrumentations-node');
+const { OTLPTraceExporter } = require('@opentelemetry/exporter-trace-otlp-grpc');
+const { OTLPMetricExporter } = require('@opentelemetry/exporter-metrics-otlp-grpc');
+const { PeriodicExportingMetricReader } = require('@opentelemetry/sdk-metrics');
+
+const otlpEndpoint = process.env.OTEL_EXPORTER_OTLP_ENDPOINT || 'http://otel-collector.monitoring:4317';
+const serviceName = process.env.OTEL_SERVICE_NAME || 'demo-app';
+
+const traceExporter = new OTLPTraceExporter({
+  url: otlpEndpoint,
+});
+
+const metricExporter = new OTLPMetricExporter({
+  url: otlpEndpoint,
+});
+
+const metricReader = new PeriodicExportingMetricReader({
+  exporter: metricExporter,
+  exportIntervalMillis: 15000,
+});
+
+const sdk = new NodeSDK({
+  serviceName,
+  traceExporter,
+  metricReader,
+  instrumentations: [
+    getNodeAutoInstrumentations({
+      '@opentelemetry/instrumentation-fs': { enabled: false },
+    }),
+  ],
+});
+
+sdk.start();
+
+process.on('SIGTERM', () => {
+  sdk.shutdown()
+    .then(() => console.log('OpenTelemetry SDK shut down'))
+    .catch((err) => console.error('Error shutting down OpenTelemetry SDK', err))
+    .finally(() => process.exit(0));
+});
+
+console.log(`OpenTelemetry initialized for service "${serviceName}" -> ${otlpEndpoint}`);