Use backend rescan summary in group editor

lib/screens/group_edit_screen.dart

@@ -80,39 +80,19 @@ class _GroupEditScreenState extends ConsumerState<GroupEditScreen> {
   }
 
   Future<void> _rescan() async {
-    final beforeIds = ref
-        .read(devicesProvider)
-        .data
-        .map((device) => device.groupMemberId)
-        .toSet();
-
     setState(() => _rescanning = true);
     try {
-      await ref.read(apiProvider).rescanNetwork();
-
-      var changed = false;
-      for (var attempt = 0; attempt < 6; attempt++) {
-        await Future.delayed(const Duration(seconds: 1));
-        await ref.read(devicesProvider.notifier).load();
-        final currentIds = ref
-            .read(devicesProvider)
-            .data
-            .map((device) => device.groupMemberId)
-            .toSet();
-        if (!_sameSet(beforeIds, currentIds)) {
-          changed = true;
-          break;
-        }
-      }
+      final response = await ref.read(apiProvider).rescanNetwork();
+      await ref.read(devicesProvider.notifier).load();
+      final summary = response.data is Map
+          ? Map<String, dynamic>.from(response.data as Map)
+          : const <String, dynamic>{};
+      final message = formatRescanSummary(summary);
 
       if (!mounted) return;
       ScaffoldMessenger.of(context).showSnackBar(
         SnackBar(
-          content: Text(
-            changed
-                ? 'Список устройств обновился'
-                : 'Сканирование завершилось, но новых устройств пока не видно',
-          ),
+          content: Text(message),
           duration: const Duration(seconds: 2),
         ),
       );
@@ -427,17 +407,31 @@ class _GroupEditScreenState extends ConsumerState<GroupEditScreen> {
     );
   }
 
-  bool _sameSet(Set<String> left, Set<String> right) {
-    if (left.length != right.length) {
-      return false;
-    }
-    for (final item in left) {
-      if (!right.contains(item)) {
-        return false;
-      }
-    }
-    return true;
+}
+
+int _summaryInt(Map<String, dynamic> summary, String key) {
+  final value = summary[key];
+  if (value is int) {
+    return value;
   }
+  return int.tryParse(value?.toString() ?? '') ?? 0;
+}
+
+String formatRescanSummary(Map<String, dynamic> summary) {
+  final found = _summaryInt(summary, 'found');
+  final added = _summaryInt(summary, 'added');
+  final updated = _summaryInt(summary, 'updated');
+  final removed = _summaryInt(summary, 'removed_offline');
+
+  if (added == 0 && updated == 0 && removed == 0 && found == 0) {
+    return 'Сканирование завершено: устройства не найдены';
+  }
+
+  if (added == 0 && removed == 0) {
+    return 'Сканирование завершено: найдено $found, обновлено $updated';
+  }
+
+  return 'Сканирование завершено: найдено $found, новых $added, обновлено $updated, убрано $removed';
 }
 
 class _ConflictBanner extends StatelessWidget {