Phase 1: data models and local storage service

- Add Models: Category, ToolItem (IsValid runtime-only, not stored), AppConfig

- Add Services: IDataService + JsonDataService (JSON load/save)

- Path validation on Load(): File.Exists check, logs warning for missing paths

- Startup: auto-calls dataService.Load() to load config

PersonalToolBox/Models/AppConfig.cs

@@ -0,0 +1,27 @@
+namespace PersonalToolBox.Models;
+
+/// <summary>
+/// 应用全局配置，对应 config.json 的顶层结构
+/// </summary>
+public class AppConfig
+{
+    /// <summary>
+    /// 主题模式 (Dark / Light)
+    /// </summary>
+    public string Theme { get; set; } = "Dark";
+
+    /// <summary>
+    /// 是否开机自启动
+    /// </summary>
+    public bool AutoStart { get; set; } = false;
+
+    /// <summary>
+    /// 工具分类列表
+    /// </summary>
+    public List<Category> Categories { get; set; } = new();
+
+    /// <summary>
+    /// 工具项列表
+    /// </summary>
+    public List<ToolItem> Tools { get; set; } = new();
+}