docs: 完善身份模块文档注释与字段说明

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

@@ -17,6 +17,12 @@ public sealed class CreateRoleCommandHandler(
     ITenantProvider tenantProvider)
     : IRequestHandler<CreateRoleCommand, RoleDto>
 {
+    /// <summary>
+    /// 处理创建角色请求。
+    /// </summary>
+    /// <param name="request">创建命令。</param>
+    /// <param name="cancellationToken">取消标记。</param>
+    /// <returns>创建后的角色 DTO。</returns>
     public async Task<RoleDto> Handle(CreateRoleCommand request, CancellationToken cancellationToken)
     {
         // 1. 获取租户上下文