implemented file thumbnails and enhanced file type icons, added reusable FileLeading widget, and updated search to support previews

lib/view/pages/files/widgets/file_details_sheet.dart

@@ -5,6 +5,7 @@ import '../../../../api/marianumcloud/webdav/queries/list_files/cacheable_file.d
 import '../../../../extensions/date_time.dart';
 import '../../../../utils/clipboard_helper.dart';
 import '../../../../widget/details_bottom_sheet.dart';
+import 'file_leading.dart';
 
 /// Shows a modal bottom sheet with technical metadata about a single file or
 /// folder: full path, MIME type, size, timestamps, ETag.
@@ -12,10 +13,7 @@ void showFileDetailsSheet(BuildContext context, CacheableFile file) {
   showDetailsBottomSheet(
     context,
     header: ListTile(
-      leading: Icon(
-        file.isDirectory ? Icons.folder : Icons.description_outlined,
-        size: 32,
-      ),
+      leading: FileLeading(file: file, size: 40),
       title: Text(
         file.name,
         style: const TextStyle(fontWeight: FontWeight.bold),

lib/view/pages/files/widgets/file_element.dart

@@ -16,6 +16,7 @@ import '../../../../widget/details_bottom_sheet.dart';
 import '../../../../widget/info_dialog.dart';
 import '../../talk/widgets/highlighted_linkify.dart';
 import 'file_details_sheet.dart';
+import 'file_leading.dart';
 
 class FileElement extends StatefulWidget {
   final CacheableFile file;
@@ -372,9 +373,7 @@ class _FileElementState extends State<FileElement> {
 
   @override
   Widget build(BuildContext context) => ListTile(
-    leading: CenteredLeading(
-      Icon(widget.file.isDirectory ? Icons.folder : Icons.description_outlined),
-    ),
+    leading: CenteredLeading(FileLeading(file: widget.file)),
     title: _title(context),
     subtitle: _subtitle(),
     trailing: Icon(widget.file.isDirectory ? Icons.arrow_right : null),

lib/view/pages/files/widgets/file_leading.dart

@@ -0,0 +1,51 @@
+import 'package:cached_network_image/cached_network_image.dart';
+import 'package:flutter/material.dart';
+
+import '../../../../api/marianumcloud/webdav/queries/list_files/cacheable_file.dart';
+import '../../../../model/account_data.dart';
+import '../../../../model/endpoint_data.dart';
+import '../data/file_type_icon.dart';
+
+/// Leading slot for a file row: shows the Nextcloud thumbnail when the
+/// server can render one (`nc:has-preview`), otherwise a typed file icon.
+/// Always reserves the same square so rows stay aligned regardless of
+/// whether a preview is present.
+class FileLeading extends StatelessWidget {
+  final CacheableFile file;
+
+  /// Edge length of the rendered square. Defaults to the regular row size;
+  /// use a larger value (e.g. in detail sheets) where appropriate.
+  final double size;
+
+  const FileLeading({required this.file, this.size = 28, super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    final icon = Icon(iconForFile(file), size: size);
+    final fileId = file.fileId;
+    return SizedBox(
+      width: size,
+      height: size,
+      child: (file.isDirectory || file.hasPreview != true || fileId == null)
+          ? Center(child: icon)
+          : ClipRRect(
+              borderRadius: BorderRadius.circular(4),
+              child: CachedNetworkImage(
+                imageUrl:
+                    'https://${EndpointData().nextcloud().full()}'
+                    '/index.php/core/preview'
+                    '?fileId=$fileId&x=128&y=128&a=0',
+                httpHeaders: AccountData().authHeaders(),
+                fit: BoxFit.cover,
+                fadeInDuration: Duration.zero,
+                fadeOutDuration: Duration.zero,
+                errorListener: (_) {},
+                // Icon doubles as the loading placeholder so the list doesn't
+                // pop a spinner per row while thumbnails stream in.
+                placeholder: (_, _) => Center(child: icon),
+                errorWidget: (_, _, _) => Center(child: icon),
+              ),
+            ),
+    );
+  }
+}