feat: add keyboard shortcuts for notes, the note list and the app

lib/main.dart

@@ -7,6 +7,7 @@ import 'package:permission_handler/permission_handler.dart';
 import 'themes/day.dart';
 import 'themes/night.dart';
 import 'note_list.dart';
+import 'shortcuts.dart';
 
 void main() async {
   WidgetsFlutterBinding.ensureInitialized();
@@ -72,6 +73,15 @@ class _MuzzleVelocityAppState extends State<MuzzleVelocityApp> {
         textTheme: GoogleFonts.ibmPlexMonoTextTheme(nightText),
       ),
       themeMode: _themeMode,
+      // App-wide shortcuts; screens can override them with their own bindings.
+      builder: (context, child) => CallbackShortcuts(
+        bindings: {
+          quitShortcut: quitApp,
+          primaryShortcut(LogicalKeyboardKey.keyD): () =>
+              _toggleTheme(_themeMode != ThemeMode.dark),
+        },
+        child: child!,
+      ),
       home: NoteListScreen(
         toggleTheme: _toggleTheme,
         toggleTags: _toggleTags,