fix: set dark theme globally to prevent white flash on page transitions

lib/main.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 import 'package:traccar_client/main_screen.dart';
 import 'package:traccar_client/permission_screen.dart';
 import 'package:traccar_client/preferences.dart';
@@ -6,6 +7,15 @@ import 'package:traccar_client/preferences.dart';
 void main() async {
   WidgetsFlutterBinding.ensureInitialized();
   await Preferences.init();
+
+  // Keep status bar dark throughout the app
+  SystemChrome.setSystemUIOverlayStyle(
+    const SystemUiOverlayStyle(
+      statusBarColor: Color(0xFF0d0d0d),
+      statusBarIconBrightness: Brightness.light,
+    ),
+  );
+
   runApp(const TraccarClientApp());
 }
 
@@ -19,8 +29,32 @@ class TraccarClientApp extends StatelessWidget {
       debugShowCheckedModeBanner: false,
       theme: ThemeData(
         useMaterial3: true,
-        colorScheme: ColorScheme.fromSeed(seedColor: Colors.blue),
-        appBarTheme: const AppBarTheme(centerTitle: true),
+        brightness: Brightness.dark,
+        scaffoldBackgroundColor: const Color(0xFF0d0d0d),
+        colorScheme: const ColorScheme.dark(
+          surface: Color(0xFF0d0d0d),
+          primary: Color(0xFF00bcd4),
+          secondary: Color(0xFF00e676),
+        ),
+        appBarTheme: const AppBarTheme(
+          centerTitle: true,
+          backgroundColor: Color(0xFF161616),
+          foregroundColor: Color(0xFFe0e0e0),
+          elevation: 0,
+        ),
+        snackBarTheme: const SnackBarThemeData(
+          backgroundColor: Color(0xFF1a1a1a),
+          contentTextStyle: TextStyle(
+            fontFamily: 'monospace',
+            color: Color(0xFFe0e0e0),
+          ),
+        ),
+        pageTransitionsTheme: const PageTransitionsTheme(
+          builders: {
+            TargetPlatform.android: ZoomPageTransitionsBuilder(),
+            TargetPlatform.iOS: CupertinoPageTransitionsBuilder(),
+          },
+        ),
       ),
       home: Preferences.permissionsGranted
           ? const MainScreen()