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/postgresql.yaml

@@ -0,0 +1,84 @@
+---
+apiVersion: v1
+kind: Secret
+metadata:
+  name: demo-postgresql
+  namespace: demo
+type: Opaque
+stringData:
+  POSTGRES_PASSWORD: demo-secret-pw
+---
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: demo-postgresql-data
+  namespace: demo
+spec:
+  accessModes:
+    - ReadWriteOnce
+  resources:
+    requests:
+      storage: 1Gi
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: demo-postgresql
+  namespace: demo
+  labels:
+    app: demo-postgresql
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: demo-postgresql
+  template:
+    metadata:
+      labels:
+        app: demo-postgresql
+    spec:
+      containers:
+        - name: postgresql
+          image: postgres:17-alpine
+          ports:
+            - containerPort: 5432
+          env:
+            - name: POSTGRES_DB
+              value: demo
+            - name: POSTGRES_USER
+              value: demo
+            - name: POSTGRES_PASSWORD
+              valueFrom:
+                secretKeyRef:
+                  name: demo-postgresql
+                  key: POSTGRES_PASSWORD
+          resources:
+            requests:
+              memory: "64Mi"
+              cpu: "50m"
+            limits:
+              memory: "128Mi"
+          volumeMounts:
+            - name: data
+              mountPath: /var/lib/postgresql/data
+              subPath: pgdata
+      volumes:
+        - name: data
+          persistentVolumeClaim:
+            claimName: demo-postgresql-data
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: demo-postgresql
+  namespace: demo
+  labels:
+    app: demo-postgresql
+spec:
+  type: ClusterIP
+  ports:
+    - port: 5432
+      targetPort: 5432
+      protocol: TCP
+  selector:
+    app: demo-postgresql