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/ToolItem.cs

@@ -0,0 +1,50 @@
+using System.Text.Json.Serialization;
+
+namespace PersonalToolBox.Models;
+
+/// <summary>
+/// 工具项模型，表示用户添加的一个可执行工具
+/// </summary>
+public class ToolItem
+{
+    /// <summary>
+    /// 工具唯一标识 (UUID)
+    /// </summary>
+    public string Id { get; set; } = Guid.NewGuid().ToString();
+
+    /// <summary>
+    /// 工具显示名称
+    /// </summary>
+    public string Name { get; set; } = string.Empty;
+
+    /// <summary>
+    /// 内置图标库的字符编码
+    /// </summary>
+    public string IconCode { get; set; } = string.Empty;
+
+    /// <summary>
+    /// 可执行文件路径或 URL
+    /// </summary>
+    public string ExecutablePath { get; set; } = string.Empty;
+
+    /// <summary>
+    /// 运行参数（选填）
+    /// </summary>
+    public string Arguments { get; set; } = string.Empty;
+
+    /// <summary>
+    /// 所属分类 ID
+    /// </summary>
+    public string CategoryId { get; set; } = string.Empty;
+
+    /// <summary>
+    /// 全局快捷键（如 Ctrl+Alt+T），选填
+    /// </summary>
+    public string HotKey { get; set; } = string.Empty;
+
+    /// <summary>
+    /// 路径是否有效（仅运行时计算，不存入 JSON）
+    /// </summary>
+    [JsonIgnore]
+    public bool IsValid { get; set; } = true;
+}