Enhance grid import/export functionality to support dynamic groups and collections

Updated the grid import/export process to allow for the inclusion of groups and collections directly from the configuration file. This enhancement ensures that missing groups and collections are created during import, improving the flexibility of the grid management system. Adjusted related classes and methods to accommodate these changes, ensuring a cohesive integration. Enhanced documentation and user prompts to clarify the new functionality and its usage.

frontend/src/features/admin/channels/components/GridTransferDialog.tsx

@@ -90,6 +90,15 @@ export function GridTransferDialog({
           skipped: result.skipped,
         }),
       )
+      // Заведённые группы упоминаем отдельно: файл от модели меняет не только сетку, и узнать
+      // об этом из общего «создано слотов» нельзя.
+      if (result.groups > 0 || result.collections > 0)
+        toast.success(
+          t('admin.channels.transfer.importedLibrary', {
+            groups: result.groups,
+            collections: result.collections,
+          }),
+        )
       onImported()
     },
     onError: (error: unknown) => {