fix: resolver advertencias de analisis i18n

lib/pantallas/pantalla_ajustes.dart

@@ -1161,6 +1161,7 @@ class _SeccionBackup extends StatelessWidget {
   const _SeccionBackup();
 
   Future<void> _exportar(BuildContext context) async {
+    final l10n = AppLocalizations.of(context);
     try {
       final estado = context.read<EstadoRadio>();
       final config = await estado.exportarConfig();
@@ -1172,17 +1173,15 @@ class _SeccionBackup extends StatelessWidget {
 
       await Share.shareXFiles(
         [XFile(file.path)],
-        subject: AppLocalizations.of(context).backupShareSubject,
-        text: AppLocalizations.of(
-          context,
-        ).backupShareText(DateTime.now().toLocal()),
+        subject: l10n.backupShareSubject,
+        text: l10n.backupShareText(DateTime.now().toLocal()),
       );
     } catch (e) {
       if (context.mounted) {
         ScaffoldMessenger.of(context).showSnackBar(
           SnackBar(
             content: Text(
-              AppLocalizations.of(context).backupExportError(e.toString()),
+              l10n.backupExportError(e.toString()),
             ),
           ),
         );
@@ -1191,6 +1190,7 @@ class _SeccionBackup extends StatelessWidget {
   }
 
   Future<void> _importar(BuildContext context) async {
+    final l10n = AppLocalizations.of(context);
     try {
       final result = await FilePicker.platform.pickFiles(
         type: FileType.custom,
@@ -1230,7 +1230,7 @@ class _SeccionBackup extends StatelessWidget {
           await estado.importarConfig(json);
           messenger.showSnackBar(
             SnackBar(
-              content: Text(AppLocalizations.of(context).backupImportSuccess),
+              content: Text(l10n.backupImportSuccess),
             ),
           );
         }
@@ -1240,7 +1240,7 @@ class _SeccionBackup extends StatelessWidget {
         ScaffoldMessenger.of(context).showSnackBar(
           SnackBar(
             content: Text(
-              AppLocalizations.of(context).backupImportError(e.toString()),
+              l10n.backupImportError(e.toString()),
             ),
           ),
         );