Added build stage

Jenkinsfile

@@ -14,6 +14,18 @@ pipeline {
             }
         }
 
+        stage('Build FlashRead CI image') {
+            steps {
+                script {
+                    def ciImage = docker.build(
+                        'fast_reader-ci:latest',
+                        '-f Dockerfile.ci .'
+                    )
+                    echo "Built CI image: ${ciImage.id}"
+                }
+            }
+        }
+
         stage('Inspect build environment') {
             steps {
                 sh '''