feat(flutter): TTL-desync toggle in the Android profile editor

Mirrors the desktop toggle: a per-profile ttlDesync flag on OstpProfile, a
SwitchListTile in the profile editor (shown for all transports, since it is the
UDP-path counterpart to the UoT-only junk/fragmentation block), and
transport.ttl_desync in the config handed to the engine, with ttl_desync_auto
true so the shared ostp-client measures the hop distance and aims the decoys
itself. The auto-calibration engine is shared, so Android already had the
capability — this just exposes the switch.

ostp-flutter/lib/models/ostp_profile.dart

@@ -23,6 +23,7 @@ class OstpProfile {
   int junkPcMax;
   int junkPsMin;
   int junkPsMax;
+  bool ttlDesync; // TTL-desync decoys (UDP), auto-calibrated in the engine
 
   OstpProfile({
     required this.id,
@@ -38,6 +39,7 @@ class OstpProfile {
     this.junkPcMax = 5,
     this.junkPsMin = 100,
     this.junkPsMax = 1000,
+    this.ttlDesync = false,
   });
 
   Map<String, dynamic> toJson() {
@@ -55,6 +57,7 @@ class OstpProfile {
       'junkPcMax': junkPcMax,
       'junkPsMin': junkPsMin,
       'junkPsMax': junkPsMax,
+      'ttlDesync': ttlDesync,
     };
   }
 
@@ -73,6 +76,7 @@ class OstpProfile {
       junkPcMax: json['junkPcMax'] as int? ?? 5,
       junkPsMin: json['junkPsMin'] as int? ?? 100,
       junkPsMax: json['junkPsMax'] as int? ?? 1000,
+      ttlDesync: json['ttlDesync'] as bool? ?? false,
     );
   }
 }

ostp-flutter/lib/ui/home_screen.dart

@@ -138,6 +138,8 @@ class _HomeScreenState extends State<HomeScreen> with TickerProviderStateMixin {
         "frag_sleep": p?.fragSleep ?? 2,
         "junk_pc": [p?.junkPcMin ?? 2, p?.junkPcMax ?? 5],
         "junk_ps": [p?.junkPsMin ?? 100, p?.junkPsMax ?? 1000],
+        "ttl_desync": p?.ttlDesync ?? false,
+        "ttl_desync_auto": true,
       },
       "multiplex": {
         "enabled": muxEnabled,

ostp-flutter/lib/ui/settings_screen.dart

@@ -224,6 +224,7 @@ class _SettingsScreenState extends State<SettingsScreen> {
     final junkPsMaxCtrl = TextEditingController(text: (profile?.junkPsMax ?? 1000).toString());
     String transportMode = profile?.transportMode ?? 'udp';
     bool tcpFragmentation = profile?.tcpFragmentation ?? false;
+    bool ttlDesync = profile?.ttlDesync ?? false;
     bool obscureKey = true;
 
     showDialog(
@@ -301,6 +302,13 @@ class _SettingsScreenState extends State<SettingsScreen> {
                       ],
                     ),
                   ],
+                  SwitchListTile(
+                    contentPadding: EdgeInsets.zero,
+                    title: const Text('TTL Desync', style: TextStyle(fontSize: 14)),
+                    subtitle: const Text('Decoy packets that die before the server (UDP, auto-tuned)', style: TextStyle(fontSize: 12, color: Colors.white54)),
+                    value: ttlDesync,
+                    onChanged: (v) => setDialogState(() => ttlDesync = v),
+                  ),
                 ],
               ),
             ),
@@ -348,6 +356,7 @@ class _SettingsScreenState extends State<SettingsScreen> {
                         junkPcMax: int.tryParse(junkPcMaxCtrl.text) ?? 5,
                         junkPsMin: int.tryParse(junkPsMinCtrl.text) ?? 100,
                         junkPsMax: int.tryParse(junkPsMaxCtrl.text) ?? 1000,
+                        ttlDesync: ttlDesync,
                       ));
                     } else {
                       profile.name = nameCtrl.text.trim().isNotEmpty ? nameCtrl.text.trim() : server;
@@ -361,6 +370,7 @@ class _SettingsScreenState extends State<SettingsScreen> {
                       profile.junkPcMax = int.tryParse(junkPcMaxCtrl.text) ?? 5;
                       profile.junkPsMin = int.tryParse(junkPsMinCtrl.text) ?? 100;
                       profile.junkPsMax = int.tryParse(junkPsMaxCtrl.text) ?? 1000;
+                      profile.ttlDesync = ttlDesync;
                     }
                     _saveProfiles();
                   });