Enhance SkillTreeNode Model to Include Additional Attributes

This commit extends the SkillTreeNode class to incorporate new attributes such as 'data', 'label', and 'shape', making the model more comprehensive. The JSON deserialization is also updated to handle optional or missing fields by providing default values, improving the robustness of the model.

frontend/lib/models/skill_tree/skill_tree_node.dart

@@ -1,18 +1,27 @@
 import 'package:auto_gpt_flutter_client/models/skill_tree/skill_node_data.dart';
 
-// TODO: Update this with actual data
 class SkillTreeNode {
   final String color;
-  final int id;
+  final SkillNodeData data;
+  final String id;
+  final String label;
+  final String shape;
 
-  // final SkillNodeData data;
-
-  SkillTreeNode({required this.color, required this.id});
+  SkillTreeNode({
+    required this.color,
+    required this.data,
+    required this.id,
+    required this.label,
+    required this.shape,
+  });
 
   factory SkillTreeNode.fromJson(Map<String, dynamic> json) {
     return SkillTreeNode(
-      color: json['color'],
-      id: json['id'],
+      color: json['color'] ?? "",
+      data: SkillNodeData.fromJson(json['data'] ?? {}),
+      id: json['id'] ?? "",
+      label: json['label'] ?? "",
+      shape: json['shape'] ?? "",
     );
   }
 }