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/k8s/service.yaml

@@ -0,0 +1,15 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: demo-app
+  namespace: demo
+  labels:
+    app: demo-app
+spec:
+  type: ClusterIP
+  ports:
+    - port: 3000
+      targetPort: 3000
+      protocol: TCP
+  selector:
+    app: demo-app