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

lib/api/marianumcloud/search/search_files_response.dart

@@ -83,9 +83,49 @@ class SearchFilesEntry {
     return null;
   }
 
+  /// Derives a filename with its extension from the WebDAV-relative path.
+  /// The provider's `title` is often the display name *without* the
+  /// extension, which would defeat extension-based icon mapping.
+  String _nameFromPath(String path) {
+    final stripped = path.replaceAll(RegExp(r'^/+|/+$'), '');
+    if (stripped.isEmpty) return title;
+    final last = stripped.split('/').last;
+    return last.isEmpty ? title : last;
+  }
+
+  /// The files search provider exposes the numeric Nextcloud file id either
+  /// as an attribute, or implicitly in the `?openfile=<id>` query parameter
+  /// of [resourceUrl]. Parses both into an [int] when available — used to
+  /// hit the preview endpoint directly.
+  int? _extractFileId() {
+    final attr = attributes?['fileId'];
+    if (attr is int) return attr;
+    if (attr is String) {
+      final parsed = int.tryParse(attr);
+      if (parsed != null) return parsed;
+    }
+    final url = resourceUrl;
+    if (url != null) {
+      final raw = Uri.tryParse(url)?.queryParameters['openfile'];
+      if (raw != null) return int.tryParse(raw);
+    }
+    return null;
+  }
+
   CacheableFile? toCacheable() {
     final path = webdavPath;
     if (path == null) return null;
-    return CacheableFile(path: path, isDirectory: isDirectory, name: title);
+    final fileId = _extractFileId();
+    return CacheableFile(
+      path: path,
+      isDirectory: isDirectory,
+      name: _nameFromPath(path),
+      fileId: fileId,
+      // Search provider responses don't carry `nc:has-preview`. Probe
+      // optimistically when a fileId is available — the preview endpoint
+      // simply returns 404 for unsupported formats, which the file-leading
+      // widget already falls back from to the typed icon.
+      hasPreview: (!isDirectory && fileId != null) ? true : null,
+    );
   }
 }