added default theme

lib/main.dart

@@ -7,6 +7,8 @@ import 'pages/main_navigation_scaffold.dart';
 import 'services/flood_station_provider.dart';
 import 'package:timezone/data/latest.dart' as tz;
 
+import 'theme.dart';
+
 void main() {
   runApp(
     ChangeNotifierProvider(
@@ -24,10 +26,7 @@ class MyApp extends StatelessWidget {
     tz.initializeTimeZones();
     return MaterialApp(
       title: 'Floodwatch',
-      theme: ThemeData(
-          colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
-          useMaterial3: true,
-          fontFamily: 'UbuntuSansMono'),
+      theme: defaultTheme,
       initialRoute: MainNavigationScaffold.routeName,
       routes: {
         MainNavigationScaffold.routeName: (context) => MainNavigationScaffold(),