added minimal error handling and user feedback

lib/pages/settings_page.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:flutter/material.dart';
 import 'package:permission_handler/permission_handler.dart';
 
@@ -43,20 +45,42 @@ class _SettingsPageState extends State<SettingsPage> {
   }
 
   void onActivateJsonExportPressed() async {
-    if (await checkStoragePermission) Storage.exportToJsonFile();
+    if (!await checkStoragePermission) return;
+
+    Storage.exportToJsonFile().then(showExportInfo);
   }
 
   void onActivateJsonImportPressed() async {
-    if (await checkStoragePermission) Storage.importFromJsonFile();
+    if (!await checkStoragePermission) return;
+    Storage.importFromJsonFile().then(showImportInfo);
   }
 
   Future<bool> get checkStoragePermission async {
     if (!(await PermissionService.requestStoragePermission).isGranted) {
       if (mounted) {
-        Notifying.showStoragePermissionErrorSnackbar(context);
+        Notifying.showErrorSnackbar(
+          context,
+          AppLocalizations.of(context)!.errorStoragePermisson,
+        );
         return false;
       }
     }
     return true;
   }
+
+  void showExportInfo(bool success) => Notifying.showSnackbar(
+    context,
+    text: success
+        ? AppLocalizations.of(context)!.exportSuccess
+        : AppLocalizations.of(context)!.exportFailed,
+    isError: success,
+  );
+
+  void showImportInfo(bool success) => Notifying.showSnackbar(
+    context,
+    text: success
+        ? AppLocalizations.of(context)!.importSuccess
+        : AppLocalizations.of(context)!.importFailed,
+    isError: success,
+  );
 }