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/frpc.js

@@ -124,9 +124,12 @@ async function startTtyd() {
     const shell = fs.existsSync('/bin/bash') ? '/bin/bash' : '/bin/sh';
     // 以普通用户身份启动 shell（与 SSH 登录一致）
     const ttydUser = process.env.CLAWD_TTY_USER || 'sts';
+    const ttyEnv = { ...process.env };
+    delete ttyEnv.NOTIFY_SOCKET;
     const proc = spawn(TTYD_BIN, ['-p', String(TTYD_PORT), '-i', '127.0.0.1', '-W', '-t', 'cursorBlink=true', '/bin/su', '-', ttydUser], {
       stdio: 'ignore',
       detached: true,
+      env: ttyEnv,
     });
     proc.unref();
     log.info('ttyd', `已启动，端口 ${TTYD_PORT}，用户=${ttydUser}`);