fix: Make transactions atomic / AutoLogout

lib/app/app.dart

@@ -2,7 +2,9 @@ import 'package:flutter/material.dart';
 import 'package:go_router/go_router.dart';
 import 'package:provider/provider.dart';
 
+import 'app_lifecycle_lock.dart';
 import '../models/settings.dart';
+import '../viewmodels/pin_lock_view_model.dart';
 import '../viewmodels/settings_view_model.dart';
 import '../theme.dart';
 import '../l10n/app_localizations.dart';
@@ -17,15 +19,28 @@ class KoolTabApp extends StatefulWidget {
 }
 
 class _KoolTabAppState extends State<KoolTabApp> {
+  late final AppLifecycleLockObserver _lifecycleLockObserver;
+
   @override
   void initState() {
     super.initState();
 
+    _lifecycleLockObserver = AppLifecycleLockObserver(
+      onLock: () => context.read<PinLockViewModel>().lock(),
+    );
+    WidgetsBinding.instance.addObserver(_lifecycleLockObserver);
+
     WidgetsBinding.instance.addPostFrameCallback((_) {
       context.read<SettingsViewModel>().ensureLoaded();
     });
   }
 
+  @override
+  void dispose() {
+    WidgetsBinding.instance.removeObserver(_lifecycleLockObserver);
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) {
     final settings = context.watch<SettingsViewModel>().settings;