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/watchdog.js

@@ -67,9 +67,13 @@ class Watchdog {
     if (this._stopped) return;
 
     log.info(this._name, '启动进程...');
+    const { env: optsEnv, ...restSpawn } = this._spawnOpts;
+    const env = { ...process.env, ...optsEnv };
+    delete env.NOTIFY_SOCKET; // 避免 frpc 等子进程向 systemd 发 notify，触发非主 PID 拒收
     const proc = spawn(this._bin, this._args, {
       stdio: ['ignore', 'pipe', 'pipe'],
-      ...this._spawnOpts,
+      ...restSpawn,
+      env,
     });
     this._proc = proc;