feat(aula-17): adicionar Cloud Native PostgreSQL (CNPG)

- Cluster PostgreSQL 3 instâncias com anti-affinity por hostname (hard)
  e por zona (soft) para spread entre datacenters Hetzner
- Backup automático via Barman Cloud para Hetzner Object Storage (S3)
- ScheduledBackup diário às 03:00
- App demo que valida conexão com o banco
- setup.sh: instala operator, cria cluster, deploya demo
- cleanup.sh: remoção limpa (backups S3 preservados)

aula-17/app-demo/deployment.yaml

@@ -0,0 +1,64 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: pg-demo
+  namespace: cnpg
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: pg-demo
+  template:
+    metadata:
+      labels:
+        app: pg-demo
+    spec:
+      containers:
+        - name: pg-demo
+          image: postgres:17
+          env:
+            - name: PGHOST
+              value: shared-postgres-rw
+            - name: PGPORT
+              value: "5432"
+            - name: PGUSER
+              value: app
+            - name: PGDATABASE
+              value: app
+            - name: PGPASSWORD
+              valueFrom:
+                secretKeyRef:
+                  name: shared-postgres-superuser
+                  key: password
+          command:
+            - /bin/bash
+            - -c
+            - |
+              echo "=== CNPG Demo App ==="
+              echo "Connecting to $PGHOST:$PGPORT/$PGDATABASE as $PGUSER..."
+
+              until pg_isready -h "$PGHOST" -p "$PGPORT" -U app -q; do
+                echo "Waiting for PostgreSQL..."
+                sleep 2
+              done
+
+              echo "Connected! Creating test table..."
+              psql -c "
+                CREATE TABLE IF NOT EXISTS visits (
+                  id SERIAL PRIMARY KEY,
+                  visited_at TIMESTAMP DEFAULT NOW(),
+                  source TEXT DEFAULT 'pg-demo'
+                );
+              "
+
+              echo "Inserting visit..."
+              psql -c "INSERT INTO visits (source) VALUES ('pg-demo');"
+
+              echo ""
+              echo "Recent visits:"
+              psql -c "SELECT * FROM visits ORDER BY id DESC LIMIT 5;"
+
+              echo ""
+              echo "=== Keeping alive. Press Ctrl+C to stop. ==="
+              echo "Connection is working! Check with: kubectl logs -f deployment/pg-demo -n cnpg"
+              sleep infinity

aula-17/app-demo/service.yaml

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+apiVersion: v1
+kind: Service
+metadata:
+  name: pg-demo
+  namespace: cnpg
+spec:
+  selector:
+    app: pg-demo
+  ports:
+    - port: 80
+      targetPort: 80
+  type: ClusterIP