Add systemd installer and non-root support

scripts/install_systemd.sh

@@ -0,0 +1,52 @@
+#!/bin/bash
+
+set -euo pipefail
+
+Server_Dir=$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)
+Service_Name="clash-for-linux"
+Service_User="${CLASH_SERVICE_USER:-clash}"
+Service_Group="${CLASH_SERVICE_GROUP:-$Service_User}"
+Unit_Path="/etc/systemd/system/${Service_Name}.service"
+
+if [ "$(id -u)" -ne 0 ]; then
+	echo -e "\033[31m[ERROR] 需要 root 权限来安装 systemd 单元\033[0m"
+	exit 1
+fi
+
+if ! getent group "$Service_Group" >/dev/null 2>&1; then
+	groupadd --system "$Service_Group"
+fi
+
+if ! id "$Service_User" >/dev/null 2>&1; then
+	useradd --system --no-create-home --shell /usr/sbin/nologin --gid "$Service_Group" "$Service_User"
+fi
+
+install -d -m 0755 "$Server_Dir/conf" "$Server_Dir/logs" "$Server_Dir/temp"
+chown -R "$Service_User:$Service_Group" "$Server_Dir/conf" "$Server_Dir/logs" "$Server_Dir/temp"
+
+cat >"$Unit_Path"<<EOF
+[Unit]
+Description=Clash for Linux
+After=network.target
+
+[Service]
+Type=simple
+WorkingDirectory=$Server_Dir
+ExecStart=/bin/bash $Server_Dir/start.sh
+ExecStop=/bin/bash $Server_Dir/shutdown.sh
+Restart=on-failure
+RestartSec=5
+User=$Service_User
+Group=$Service_Group
+PIDFile=$Server_Dir/temp/clash.pid
+Environment=CLASH_ENV_FILE=$Server_Dir/temp/clash-for-linux.sh
+
+[Install]
+WantedBy=multi-user.target
+EOF
+
+systemctl daemon-reload
+
+echo -e "\033[32m[OK] 已生成 systemd 单元: ${Unit_Path}\033[0m"
+echo -e "可执行以下命令启动服务："
+echo -e "  sudo systemctl enable --now ${Service_Name}.service"