feat: redesign and lots of progress

lib/main.dart

@@ -1,3 +1,6 @@
+import 'dart:async';
+
+import 'package:abawo_bt_app/controller/bluetooth.dart';
 import 'package:abawo_bt_app/pages/devices_page.dart';
 import 'package:abawo_bt_app/pages/devices_tab_page.dart';
 import 'package:abawo_bt_app/src/rust/frb_generated.dart';
@@ -29,11 +32,47 @@ Future<void> main() async {
   ], child: const AbawoBtApp()));
 }
 
-class AbawoBtApp extends ConsumerWidget {
+class AbawoBtApp extends ConsumerStatefulWidget {
   const AbawoBtApp({super.key});
 
   @override
-  Widget build(BuildContext context, WidgetRef ref) {
+  ConsumerState<AbawoBtApp> createState() => _AbawoBtAppState();
+}
+
+class _AbawoBtAppState extends ConsumerState<AbawoBtApp>
+    with WidgetsBindingObserver {
+  @override
+  void initState() {
+    super.initState();
+    WidgetsBinding.instance.addObserver(this);
+  }
+
+  @override
+  void dispose() {
+    WidgetsBinding.instance.removeObserver(this);
+    super.dispose();
+  }
+
+  @override
+  void didChangeAppLifecycleState(AppLifecycleState state) {
+    if (state == AppLifecycleState.hidden ||
+        state == AppLifecycleState.paused) {
+      unawaited(_disconnectBluetoothForBackground());
+    }
+  }
+
+  Future<void> _disconnectBluetoothForBackground() async {
+    final bluetooth = ref.read(bluetoothProvider).value;
+    if (bluetooth == null) {
+      return;
+    }
+
+    await bluetooth.stopScan();
+    await bluetooth.disconnect();
+  }
+
+  @override
+  Widget build(BuildContext context) {
     final themePreference = ref.watch(appThemePreferenceProvider);
 
     return MaterialApp.router(