simplified code across the app and consolidated duplicated helpers

lib/view/pages/files/data/file_sort.dart

@@ -0,0 +1,25 @@
+import '../../../../api/marianumcloud/webdav/queries/list_files/cacheable_file.dart';
+import '../../../../api/marianumcloud/webdav/queries/list_files/list_files_response.dart';
+import '../../../../state/app/modules/settings/bloc/settings_cubit.dart';
+import 'sort_options.dart';
+
+typedef FileSort = ({SortOption by, bool ascending, bool foldersToTop});
+
+/// Selector for `context.select`, so folder views rebuild only when the
+/// file sort settings change.
+FileSort fileSortOf(SettingsCubit cubit) {
+  final settings = cubit.state.fileSettings;
+  return (
+    by: settings.sortBy,
+    ascending: settings.ascending,
+    foldersToTop: settings.sortFoldersToTop,
+  );
+}
+
+extension FileSortListing on ListFilesResponse {
+  List<CacheableFile> sortedBy(FileSort sort) => sortBy(
+    sortOption: sort.by,
+    foldersToTop: sort.foldersToTop,
+    reversed: sort.ascending,
+  );
+}

lib/view/pages/files/data/file_type_icon.dart

@@ -11,12 +11,7 @@ IconData iconForFile(CacheableFile file) {
     final byMime = _iconForMime(mime);
     if (byMime != null) return byMime;
   }
-  final ext = _extensionOf(file.name);
-  if (ext != null) {
-    final byExt = _extensionIcons[ext];
-    if (byExt != null) return byExt;
-  }
-  return Icons.insert_drive_file_outlined;
+  return iconForFileName(file.name);
 }
 
 /// Icon for a bare file name (no [CacheableFile] / MIME available), e.g. in the

lib/view/pages/files/data/webdav_path.dart

@@ -0,0 +1,26 @@
+// Paths relative to the WebDAV root, as used by `CacheableFile.path`: no
+// leading slash, folders end with '/', the root folder is ''.
+
+final RegExp _edgeSlashes = RegExp(r'^/+|/+$');
+
+List<String> webdavSegmentsOf(String path) {
+  final stripped = path.replaceAll(_edgeSlashes, '');
+  return stripped.isEmpty ? [] : stripped.split('/');
+}
+
+List<String> webdavParentSegmentsOf(String path) {
+  final segments = webdavSegmentsOf(path);
+  if (segments.isNotEmpty) segments.removeLast();
+  return segments;
+}
+
+String webdavFolderPath(List<String> segments) =>
+    segments.isEmpty ? '' : '${segments.join('/')}/';
+
+String webdavJoin(String folder, String name, {required bool isDirectory}) =>
+    isDirectory ? '$folder$name/' : '$folder$name';
+
+/// Folder key used by `ListFilesCache` and `FilesBloc`: no leading or
+/// trailing slash, root is '/'.
+String listFilesCacheKey(List<String> segments) =>
+    segments.isEmpty ? '/' : segments.join('/');