fix: deploy.sh蓝绿部署时service文件路径按target区分(common.sh get_service_file_local)

lib/common.sh

@@ -63,7 +63,14 @@ EOF
 }
 
 # ---------- 环境配置（systemd service）----------
-get_service_file_local() { echo "${SCRIPT_DIR}/deploy/rust-backend-${APP_ENV}.service"; }
+get_service_file_local() {
+    local target="${BG_TARGET:-}"
+    if [ -n "$target" ]; then
+        echo "${SCRIPT_DIR}/deploy/rust-backend-${target}.service"
+    else
+        echo "${SCRIPT_DIR}/deploy/rust-backend-${APP_ENV}.service"
+    fi
+}
 
 check_service_file() {
     log_step "检查远程 systemd service 文件..."