Deck list work

SVSim.EmulatedEntrypoint/Models/Dtos/ColosseumSalesPeriodInfo.cs

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+using MessagePack;
+using System.Text.Json.Serialization;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos;
+
+/// <summary>
+/// Nested under /mypage/index data.colosseum_info.sales_period_info. Carries the wall-clock end of
+/// the current cup's sales window. Captured from prod:
+/// <c>"sales_period_info": { "sales_period_time": "2026-05-25 19:59:59" }</c>.
+/// </summary>
+[MessagePackObject]
+public class ColosseumSalesPeriodInfo
+{
+    /// <summary>Wire format is "yyyy-MM-dd HH:mm:ss" (prod's PHP convention, not ISO).</summary>
+    [JsonPropertyName("sales_period_time")]
+    [Key("sales_period_time")]
+    public string SalesPeriodTime { get; set; } = string.Empty;
+}