彻底修复cp目标不是目录问题：先删除旧dist再重建目录

deploy.sh

@@ -22,8 +22,8 @@ cd ..
 
 # 4. 部署前端资源...
 echo "4. 部署前端资源..."
+rm -rf backend/dist
 mkdir -p backend/dist
-rm -rf backend/dist/*
 cp -rf frontend/dist/* backend/dist/
 
 # 5. 创建systemd服务