ci(jenkins): deploy stages run in standalone pipeline job (BRANCH_NAME unset)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Jenkinsfile

@@ -45,7 +45,7 @@ pipeline {
     }
 
     stage('Inject Env (Secret File)') {
-      when { anyOf { branch 'main'; branch 'dev' } }
+      when { expression { !env.BRANCH_NAME || env.BRANCH_NAME in ['main', 'dev'] } }
       steps {
         script {
           // Backend 패턴과 동일: 브랜치별로 Jenkins Secret File 주입
@@ -68,7 +68,7 @@ pipeline {
     }
 
     stage('Deploy') {
-      when { anyOf { branch 'main'; branch 'dev' } }
+      when { expression { !env.BRANCH_NAME || env.BRANCH_NAME in ['main', 'dev'] } }
       steps {
         script { deployFrontend() }
       }