install_linux.sh: support DEPLOY_BRANCH env var for non-main branch deployment

Usage: sudo DEPLOY_BRANCH=debug-logging bash install_linux.sh

install_linux.sh

@@ -14,9 +14,13 @@ if [ "$(id -u)" -ne 0 ]; then
     exit 1
 fi
 
-echo ">>> 拉取最新代码（强制覆盖本地修改）..."
+# 部署分支（默认 main，调试时可改为其他分支如 debug-logging）
+DEPLOY_BRANCH="${DEPLOY_BRANCH:-main}"
+
+echo ">>> 拉取最新代码（分支: $DEPLOY_BRANCH，强制覆盖本地修改）..."
 git fetch origin
-git reset --hard origin/main
+git checkout "$DEPLOY_BRANCH"
+git reset --hard "origin/$DEPLOY_BRANCH"
 
 echo ">>> 安装前端依赖并构建..."
 cd frontend