fix(session): don't release the session on a SOCKS5 Reconnect

Regression from e67f0b9, shipped in 3.3.7.

Reconnect repairs an orphaned proxy by tearing the runtime down and
re-attaching to the session the device already holds. It does that
through SessionTimer.disconnect(), which e67f0b9 taught to hand the
session back to the server - so it destroyed the very session the
following connect(resume: true) then asked for. Unawaited, so it raced:
the resume either found the session already gone or removed moments
later, surfacing as "Session not activated".

disconnect() now takes release, and the Reconnect path passes false.
Every other caller still hands the session back.

Narrow in practice: SOCKS5 mode only, only the Settings Reconnect
button, and the main-screen connect was unaffected because it mints a
new session anyway.

Co-Authored-By: Claude Opus 5 <[email protected]>

lib/screens/settings/in_settings/connection_mode.dart

@@ -76,7 +76,7 @@ class _ConnectionModeTileState extends State<ConnectionModeTile> {
 
     setState(() => _reconnecting = true);
     try {
-      await timer.disconnect();
+      await timer.disconnect(release: false);
       if (!mounted) return;
       if (await vpn.connect(resume: true)) {
         if (!mounted) return;