ci: use Docker agent for Maven build stage on Windows Jenkins

Run mvn inside maven:3.9-eclipse-temurin-21 Linux container via Docker
Pipeline plugin; Docker/SSH deploy stages remain on native agent so
Docker Desktop socket is available for image push and SSH for deploy.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Jenkinsfile

@@ -1,5 +1,5 @@
 pipeline {
-  agent any
+  agent none
 
   parameters {
     choice(name: 'SERVICE', choices: ['tenant-service', 'im-service', 'push-service', 'update-service'], description: '要构建的服务模块')
@@ -18,21 +18,31 @@ pipeline {
 
   stages {
     stage('Checkout') {
+      agent any
       steps {
         checkout scm
+        stash name: 'source', includes: '**/*'
       }
     }
 
     stage('Build JAR') {
+      agent {
+        docker {
+          image 'maven:3.9-eclipse-temurin-21'
+          args '-v maven-repo:/root/.m2'
+        }
+      }
       steps {
-        sh """
-          mvn -pl ${params.SERVICE} -am -DskipTests -q clean package
-        """
+        unstash 'source'
+        sh "mvn -pl ${params.SERVICE} -am -DskipTests -q clean package"
+        stash name: 'jar', includes: "${params.SERVICE}/target/*.jar,${params.SERVICE}/Dockerfile,Dockerfile"
       }
     }
 
     stage('Docker Build & Push') {
+      agent any
       steps {
+        unstash 'jar'
         withCredentials([string(credentialsId: 'ACR_PASSWORD', variable: 'ACR_PASS')]) {
           script {
             def imageName = "${ACR_REGISTRY}/${ACR_NAMESPACE}/${params.SERVICE}:${params.IMAGE_TAG}"
@@ -48,6 +58,7 @@ pipeline {
     }
 
     stage('Deploy to Production') {
+      agent any
       when { expression { return params.DEPLOY } }
       steps {
         withCredentials([sshUserPrivateKey(credentialsId: 'PROD_SSH_KEY', keyFileVariable: 'SSH_KEY')]) {