new: add seperated VPN service mode

lib/singbox/model/singbox_config_enum.dart

@@ -6,7 +6,8 @@ import 'package:json_annotation/json_annotation.dart';
 enum ServiceMode {
   proxy("proxy"),
   systemProxy("system-proxy"),
-  tun("vpn");
+  tun("vpn"),
+  tunService("vpnService");
 
   const ServiceMode(this.key);
 
@@ -27,6 +28,8 @@ enum ServiceMode {
         systemProxy => t.settings.config.serviceModes.systemProxy,
         tun =>
           "${t.settings.config.serviceModes.tun}${PlatformUtils.isDesktop ? " (${t.settings.experimental})" : ""}",
+        tunService =>
+          "${t.settings.config.serviceModes.tunService}${PlatformUtils.isDesktop ? " (${t.settings.experimental})" : ""}",
       };
 }
 

lib/singbox/model/singbox_config_option.dart

@@ -33,6 +33,7 @@ class SingboxConfigOption with _$SingboxConfigOption {
     required bool enableClashApi,
     required int clashApiPort,
     required bool enableTun,
+    required bool enableTunService,
     required bool setSystemProxy,
     required bool bypassLan,
     required bool allowConnectionFromLan,