feat(ground-suite): add theme selector

ground-suite/lib/app/app.dart

@@ -1,19 +1,21 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import 'app_shell.dart';
 import 'theme.dart';
+import 'theme_mode_controller.dart';
 
-class GroundSuiteApp extends StatelessWidget {
+class GroundSuiteApp extends ConsumerWidget {
   const GroundSuiteApp({super.key});
 
   @override
-  Widget build(BuildContext context) {
+  Widget build(BuildContext context, WidgetRef ref) {
     return MaterialApp(
       title: 'Ground Suite',
       debugShowCheckedModeBanner: false,
       theme: groundSuiteLightTheme(),
       darkTheme: groundSuiteDarkTheme(),
-      themeMode: ThemeMode.system,
+      themeMode: ref.watch(themeModeProvider),
       home: const AppShell(),
     );
   }