fix(tunnel-node): revert LONGPOLL_DEADLINE to 2s

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: yyoyoian-pixel

tunnel-node/src/main.rs

@@ -71,7 +71,7 @@ const STRAGGLER_SETTLE_MAX: Duration = Duration::from_millis(1000);
 /// `BATCH_TIMEOUT` (30 s) and Apps Script's UrlFetch ceiling (~60 s).
 /// Tested on censored networks in Iran where users reported smoother
 /// Telegram video playback and fewer session resets at this value.
-const LONGPOLL_DEADLINE: Duration = Duration::from_secs(4);
+const LONGPOLL_DEADLINE: Duration = Duration::from_secs(2);
 
 /// Bound on each UDP session's inbound queue. Beyond this we drop oldest
 /// to keep recent voice/media packets moving — a stale RTP frame is