fix(settings): export string-list preferences after a cold start

Match the tolerant list predicate the import path already uses. The platform
preference cache returns List<Object?> after a restart, so the exact
List<String> pattern silently dropped tracker library filter ids and a
restored profile resumed scrobbling libraries the user had excluded.

lib/services/settings_export_service.dart

@@ -195,7 +195,10 @@ class SettingsExportService {
       _typeInt when value is int => {'type': _typeInt, 'value': value},
       _typeDouble when value is double => {'type': _typeDouble, 'value': value},
       _typeString when value is String => {'type': _typeString, 'value': value},
-      _typeStringList when value is List<String> => {'type': _typeStringList, 'value': value},
+      _typeStringList when _isValidValue(_typeStringList, value) => {
+        'type': _typeStringList,
+        'value': (value! as List).cast<String>().toList(),
+      },
       _ => null,
     };
   }

test/services/settings_export_service_test.dart

@@ -178,6 +178,25 @@ void main() {
       expect(exported.keys.where((key) => key.startsWith('tvos_db_recovery_')), isEmpty);
       expect(encoded, isNot(contains(canary)));
     });
+    test('exports cold-start string lists while rejecting lists with non-string elements', () async {
+      resetSharedPreferencesForTest(
+        initialAsync: {
+          'tracker_library_filter_mode_trakt': 'blacklist',
+          'tracker_library_filter_ids_trakt': <Object?>['srv-1:lib-a', 'srv-1:lib-b'],
+          'tracker_library_filter_ids_simkl': <Object?>['ok', 7],
+        },
+      );
+      final prefs = await BaseSharedPreferencesService.sharedCache();
+
+      final exported =
+          SettingsExportService.buildExportMap(prefs, currentUserUuid: 'alice')['prefs'] as Map<String, dynamic>;
+
+      expect(exported['tracker_library_filter_ids_trakt'], {
+        'type': 'stringList',
+        'value': ['srv-1:lib-a', 'srv-1:lib-b'],
+      });
+      expect(exported, isNot(contains('tracker_library_filter_ids_simkl')));
+    });
   });
 
   group('transactional import', () {