chore: update Android SDK version in local.properties and clean up JSON response schema; enhance step5_page with horizontal scroll direction and reverse order

packages/core/lib/presentation/widget/slider/logic.dart

@@ -4,8 +4,11 @@ import 'package:flutter/material.dart';
 import 'package:rasadyar_core/core.dart';
 
 class SliderLogic extends GetxController with StateMixin<List<String>> {
-  final PageController pageController = PageController(initialPage: 0, viewportFraction: .93);
-  late Timer _timer;
+  final PageController pageController = PageController(
+    initialPage: 0,
+    viewportFraction: .93,
+  );
+  Timer? _timer;
   late Duration duration;
 
   @override
@@ -33,7 +36,7 @@ class SliderLogic extends GetxController with StateMixin<List<String>> {
 
   @override
   void onClose() {
-    _timer.cancel();
+    _timer?.cancel();
     pageController.dispose();
     super.onClose();
   }