Add preflight checks in Jenkinsfile to ensure Docker is installed on the agent before proceeding with the pipeline, improving error handling and setup validation.

Jenkinsfile

@@ -1,5 +1,7 @@
 pipeline {
-  agent any
+  agent {
+    label 'any'
+  }
 
   options {
     timestamps()
@@ -17,6 +19,21 @@ pipeline {
   }
 
   stages {
+    stage('Preflight tools') {
+      steps {
+        sh '''
+          set -euo pipefail
+          echo "Node: $(hostname)"
+          if ! command -v docker >/dev/null 2>&1; then
+            echo "ERROR: este agente no tiene docker instalado."
+            echo "Usa un nodo Jenkins con label 'docker' y acceso al daemon."
+            exit 1
+          fi
+          docker --version
+        '''
+      }
+    }
+
     stage('Checkout') {
       steps {
         checkout([