fix(rollback): Fix bash loop syntax for health check retries

apps/demo-nginx/Jenkinsfile.rollback

@@ -242,7 +242,9 @@ pipeline {
                 script {
                     echo "🏥 Running health checks..."
                     
-                    sh """
+                    sh """#!/bin/bash
+                        set -e
+                        
                         # Check all pods are ready
                         READY_PODS=\$(kubectl get deployment ${APP_NAME} -n ${NAMESPACE} -o jsonpath='{.status.readyReplicas}')
                         DESIRED_PODS=\$(kubectl get deployment ${APP_NAME} -n ${NAMESPACE} -o jsonpath='{.spec.replicas}')
@@ -263,14 +265,16 @@ pipeline {
                         echo "Testing pod: \${POD_NAME}"
                         
                         # Test health endpoint with retry
-                        for i in {1..5}; do
+                        for i in 1 2 3 4 5; do
                             echo "Health check attempt \$i/5..."
                             if kubectl exec \${POD_NAME} -n ${NAMESPACE} -- wget -q -O- http://localhost/health 2>/dev/null; then
                                 echo "✅ Health check passed!"
                                 exit 0
                             fi
+                            if [ \$i -lt 5 ]; then
                                 echo "Retrying in 5 seconds..."
                                 sleep 5
+                            fi
                         done
                         
                         echo "❌ Health check failed after 5 attempts"