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/package.json

@@ -0,0 +1,17 @@
+{
+  "name": "demo-app",
+  "version": "1.0.0",
+  "description": "Demo app for APM with OpenTelemetry - Workshop Aula 15",
+  "main": "app.js",
+  "scripts": {
+    "start": "node --require ./tracing.js app.js"
+  },
+  "dependencies": {
+    "express": "^4.21.2",
+    "pg": "^8.13.1",
+    "@opentelemetry/sdk-node": "^0.57.2",
+    "@opentelemetry/auto-instrumentations-node": "^0.56.1",
+    "@opentelemetry/exporter-trace-otlp-grpc": "^0.57.2",
+    "@opentelemetry/exporter-metrics-otlp-grpc": "^0.57.2"
+  }
+}