Add SkillNodeData data model for skill tree

The SkillNodeData model aggregates various data related to a skill node.
It includes:
- Node name
- Node category
- Associated task
- Dependencies
- Cutoff value
- Ground object for evaluation details
- Info object for metadata

frontend/lib/models/skill_tree/skill_node_data.dart

@@ -0,0 +1,34 @@
+import 'package:auto_gpt_flutter_client/models/skill_tree/ground.dart';
+import 'package:auto_gpt_flutter_client/models/skill_tree/info.dart';
+
+class SkillNodeData {
+  final String name;
+  final List<String> category;
+  final String task;
+  final List<String> dependencies;
+  final int cutoff;
+  final Ground ground;
+  final Info info;
+
+  SkillNodeData({
+    required this.name,
+    required this.category,
+    required this.task,
+    required this.dependencies,
+    required this.cutoff,
+    required this.ground,
+    required this.info,
+  });
+
+  factory SkillNodeData.fromJson(Map<String, dynamic> json) {
+    return SkillNodeData(
+      name: json['name'],
+      category: List<String>.from(json['category']),
+      task: json['task'],
+      dependencies: List<String>.from(json['dependencies']),
+      cutoff: json['cutoff'],
+      ground: Ground.fromJson(json['ground']),
+      info: Info.fromJson(json['info']),
+    );
+  }
+}