implemented Nextcloud file previews for unknown file types using fileId and has-preview flags, updated file models, and refined manual refresh logic.

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

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:collection/collection.dart';
 
 import '../../../../../api/errors/error_mapper.dart';
@@ -42,6 +44,16 @@ class FilesBloc
     await _query(path, renew: true);
   }
 
+  /// LoadableState.reFetch (used by the pull-to-refresh indicator and the
+  /// error-screen retry button) routes through here. The inherited retry()
+  /// goes via gatherData() which respects the cache TTL — for an explicit
+  /// user-initiated reload we must bypass it, otherwise the root listing
+  /// silently returns its day-old cached payload without hitting the server.
+  @override
+  void retry() {
+    unawaited(refresh());
+  }
+
   Future<void> setPath(List<String> path) async {
     add(Emit((s) => s.copyWith(currentPath: path, listing: null)));
     add(RefetchStarted<FilesState>());