feat(net): late uplink poll + faster provision monitor (15s)

- client: while !_connectionStarted, poll every 3s for hasInternet or
  hasWiredInternetProbe (e.g. Ethernet after AP); start _proceedWithConnection
  once; clear poll on network-ready/stop. Avoids provision-level emit spam.
- provisioning: MONITOR_INTERVAL_MS 30s -> 15s for quicker WiFi/AP UI.

Made-with: Cursor

lib/provisioning.js

@@ -7,7 +7,7 @@ const { DnsHijack }    = require('./dns-hijack');
 const { CaptiveServer } = require('./captive-server');
 const led = require('./led');
 
-const MONITOR_INTERVAL_MS = 30_000;
+const MONITOR_INTERVAL_MS = 15_000;
 const BOOT_WAIT_MAX_MS    = 20_000; // 等待 NM 自动连接的最大时间
 const BOOT_POLL_MS        = 2_000;  // 轮询间隔