fixes before build 2

lib/services/backup_format.dart

@@ -5,6 +5,9 @@ import 'dart:convert';
 
 const int kBackupVersion = 3;
 
+const String kBackupFormat = 'groci-backup';
+const String kLegacyBackupFormat = 'receipity-backup';
+
 class BackupDocument {
   const BackupDocument({
     required this.version,
@@ -33,7 +36,7 @@ class BackupDocument {
   final Map<String, String> images;
 
   Map<String, Object?> toJson() => {
-    'format': 'receipity-backup',
+    'format': kBackupFormat,
     'version': version,
     'exportedAt': exportedAt,
     'darkMode': darkMode,
@@ -54,8 +57,9 @@ class BackupDocument {
     if (decoded is! Map<String, dynamic>) {
       throw const FormatException('Backup is not a JSON object.');
     }
-    if (decoded['format'] != 'receipity-backup') {
-      throw const FormatException('This file is not a Receipity backup.');
+    final format = decoded['format'];
+    if (format != kBackupFormat && format != kLegacyBackupFormat) {
+      throw const FormatException('This file is not a Groci backup.');
     }
     final version = decoded['version'];
     if (version is! int || version < 1 || version > kBackupVersion) {