feat: 添加用户权限洞察查询与示例

src/Application/TakeoutSaaS.Application/Identity/Queries/GetUserPermissionsQuery.cs

@@ -0,0 +1,15 @@
+using MediatR;
+using TakeoutSaaS.Application.Identity.Contracts;
+
+namespace TakeoutSaaS.Application.Identity.Queries;
+
+/// <summary>
+/// 按用户 ID 获取角色/权限概览。
+/// </summary>
+public sealed class GetUserPermissionsQuery : IRequest<UserPermissionDto?>
+{
+    /// <summary>
+    /// 用户 ID（雪花）。
+    /// </summary>
+    public long UserId { get; init; }
+}