added support for simultan downloads in files and talk, support for background downloads, enhanced loading in files with retry

lib/state/app/modules/files/bloc/files_bloc.dart

@@ -96,6 +96,10 @@ class FilesBloc
           );
           add(Emit((s) => s.copyWith(listing: cached)));
         },
+        onRetry: (next, max) {
+          if (isStale()) return;
+          add(LoadingStatus('Erneuter Versuch ($next von $max) …'));
+        },
         onError: (e) => capturedError = e,
       );
     } catch (e) {

lib/state/app/modules/files/data_provider/files_data_provider.dart

@@ -21,6 +21,7 @@ class FilesDataProvider {
     void Function(ListFilesResponse)? onCacheData,
     void Function(Object)? onError,
     bool renew = false,
+    void Function(int nextAttempt, int maxAttempts)? onRetry,
   }) => resolveFromCache<ListFilesResponse>(
     (onUpdate, onError) => ListFilesCache(
       path: path,
@@ -28,6 +29,7 @@ class FilesDataProvider {
       onCacheData: onCacheData,
       onError: onError,
       renew: renew,
+      onRetry: onRetry,
     ),
     onError: onError,
     operationName: 'listFiles',