fix(knowledgebase): parsing for knowledge

lib/core/models/knowledge_base_file.dart

@@ -0,0 +1,54 @@
+import 'package:freezed_annotation/freezed_annotation.dart';
+
+import '../utils/json_parsing.dart';
+
+part 'knowledge_base_file.freezed.dart';
+
+/// A file within a knowledge base.
+///
+/// The new WebUI API returns files from a dedicated endpoint with pagination.
+/// Files are deduplicated by content hash (not filename).
+@freezed
+sealed class KnowledgeBaseFile with _$KnowledgeBaseFile {
+  const factory KnowledgeBaseFile({
+    required String id,
+    required String filename,
+    Map<String, dynamic>? meta,
+    required DateTime createdAt,
+    DateTime? updatedAt,
+
+    /// Content hash used for server-side deduplication.
+    String? contentHash,
+  }) = _KnowledgeBaseFile;
+
+  /// Creates a [KnowledgeBaseFile] from JSON, handling various API formats.
+  factory KnowledgeBaseFile.fromJson(Map<String, dynamic> json) {
+    return KnowledgeBaseFile(
+      id: json['id'] as String,
+      filename: _extractFilename(json),
+      meta: json['meta'] as Map<String, dynamic>?,
+      createdAt: parseDateTime(json['created_at'] ?? json['createdAt']),
+      updatedAt: parseDateTimeOrNull(json['updated_at'] ?? json['updatedAt']),
+      contentHash:
+          (json['hash'] ?? json['content_hash'] ?? json['contentHash'])
+              as String?,
+    );
+  }
+}
+
+/// Extracts filename from various possible locations in the JSON.
+String _extractFilename(Map<String, dynamic> json) {
+  if (json.containsKey('filename')) {
+    return json['filename'] as String? ?? 'Unknown';
+  }
+  if (json.containsKey('name')) {
+    return json['name'] as String? ?? 'Unknown';
+  }
+  // Check nested meta object
+  final meta = json['meta'];
+  if (meta is Map) {
+    final name = meta['name'] ?? meta['filename'];
+    if (name is String) return name;
+  }
+  return 'Unknown';
+}