feat(app): OS session-expiry enforcement, session persistence, support sync

Enforce session expiry at the OS level (AlarmManager + handler) so the tunnel dies even if the UI process is killed; persist the session so a START_STICKY restart re-establishes it; sync immediately after a support top-up; slow the session beacon 5s/30s -> 60s/60s; drop the Always-on-VPN deep-link and the legacy 'ass' migration. Docs: CHANGELOG 3.3.4, privacy-policy log disclosure, README.

lib/components/support_button.dart

@@ -34,6 +34,7 @@ class _SupportButtonState extends State<SupportButton> {
       final rewarded = await ad.showAd('support');
       if (rewarded) {
         await timer.markSupportRewardClaimed();
+        await timer.syncNow();
       }
     } finally {
       if (mounted) setState(() => _busy = false);