docs: 完善身份模块文档注释与字段说明

src/Application/TakeoutSaaS.Application/Identity/Handlers/PermissionTreeQueryHandler.cs

@@ -14,6 +14,12 @@ public sealed class PermissionTreeQueryHandler(
     ITenantProvider tenantProvider)
     : IRequestHandler<PermissionTreeQuery, IReadOnlyList<PermissionTreeDto>>
 {
+    /// <summary>
+    /// 构建权限树。
+    /// </summary>
+    /// <param name="request">查询参数。</param>
+    /// <param name="cancellationToken">取消标记。</param>
+    /// <returns>权限树列表。</returns>
     public async Task<IReadOnlyList<PermissionTreeDto>> Handle(PermissionTreeQuery request, CancellationToken cancellationToken)
     {
         // 1. 获取租户上下文并查询权限