fix(network): wired ping probe, AP/WS and systemd notify hardening

- Add hasWiredInternetProbe and export; AP mode uses it with hasInternet
- systemd-env: strip NOTIFY_SOCKET from env early; client uses unix_dgram
- Strip NOTIFY_SOCKET from frpc/ttyd spawn env in watchdog and frpc
- WS: pong miss debounce; AP net monitor consecutive-fail debounce

Made-with: Cursor

lib/systemd-env.js

@@ -0,0 +1,17 @@
+'use strict';
+
+/**
+ * 在任意子进程（nmcli、pkill、frpc、依赖库）启动前，从 process.env 摘掉 NOTIFY_SOCKET。
+ * 否则子进程继承后可能向 systemd 发 sd_notify，触发「仅主 PID 可收」的 journal 刷屏。
+ * 主进程通过 getNotifySocket() 取回路径，自行 unix_dgram 发送。
+ */
+const _notifySocket = process.env.NOTIFY_SOCKET;
+if (_notifySocket) {
+  delete process.env.NOTIFY_SOCKET;
+}
+
+function getNotifySocket() {
+  return _notifySocket;
+}
+
+module.exports = { getNotifySocket };