feat: cellular-proxy 一键安装 — 走代理一律数据出口

- sing-box 单进程 bind 数据网卡
- mixed HTTP+SOCKS + 中文静态面板
- install.sh 支持 curl | sudo bash
- 512MB 友好 MemoryMax 默认 96MB

systemd/cellular-proxy.service

@@ -0,0 +1,24 @@
+[Unit]
+Description=cellular-proxy (sing-box dual-WAN split, Chinese UI)
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+EnvironmentFile=-@INSTALL_DIR@/etc/runtime.env
+ExecStartPre=/bin/mkdir -p /var/lib/cellular-proxy @LOG_DIR@
+ExecStart=@INSTALL_DIR@/bin/sing-box run -c @INSTALL_DIR@/etc/config.json
+Restart=on-failure
+RestartSec=3
+LimitNOFILE=65535
+# 低内存设备软上限（install 时替换；0 则删除本行）
+MemoryMax=@MEMORY_MAX@
+NoNewPrivileges=true
+ProtectSystem=full
+ProtectHome=true
+PrivateTmp=true
+StandardOutput=append:@LOG_DIR@/stdout.log
+StandardError=append:@LOG_DIR@/stderr.log
+
+[Install]
+WantedBy=multi-user.target