revert: back to GTK defaults like original Hiddify

lib/main.dart

@@ -1,55 +1,9 @@
-import 'dart:io';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:umbrix/bootstrap.dart';
 import 'package:umbrix/core/model/environment.dart';
 
 void main() async {
-  // Single instance check - BEFORE Flutter initialization
-  if (Platform.isLinux || Platform.isWindows) {
-    final lockFile = File('/tmp/umbrix.lock');
-    
-    if (await lockFile.exists()) {
-      try {
-        final pidString = await lockFile.readAsString();
-        final pid = int.tryParse(pidString.trim());
-        
-        if (pid != null) {
-          // Check if process is still alive
-          final result = await Process.run('ps', ['-p', pid.toString()]);
-          
-          if (result.exitCode == 0) {
-            // Process alive - restore and focus existing window
-            try {
-              // Find window and restore from minimized state, then activate
-              final searchResult = await Process.run('xdotool', ['search', '--name', 'Umbrix']);
-              if (searchResult.exitCode == 0 && searchResult.stdout.toString().trim().isNotEmpty) {
-                final windowId = searchResult.stdout.toString().trim().split('\n').first;
-                // Restore from minimized/iconified state
-                await Process.run('xdotool', ['windowmap', windowId]);
-                await Process.run('xdotool', ['windowactivate', windowId]);
-              }
-            } catch (_) {
-              // xdotool not available, just exit
-            }
-            exit(0);
-          } else {
-            // Stale lock - remove it
-            await lockFile.delete();
-          }
-        }
-      } catch (e) {
-        try { await lockFile.delete(); } catch (_) {}
-      }
-    }
-    
-    // Create lock file with current PID
-    try {
-      await lockFile.create();
-      await lockFile.writeAsString(pid.toString());
-    } catch (_) {}
-  }
-
   final widgetsBinding = WidgetsFlutterBinding.ensureInitialized();
 
   SystemChrome.setEnabledSystemUIMode(SystemUiMode.edgeToEdge);

linux/my_application.cc

@@ -137,6 +137,6 @@ MyApplication *my_application_new()
 {
   return MY_APPLICATION(g_object_new(my_application_get_type(),
                                      "application-id", APPLICATION_ID,
-                                     "flags", G_APPLICATION_NON_UNIQUE,
+                                     "flags", G_APPLICATION_DEFAULT_FLAGS,
                                      nullptr));
 }