feat(tutorial): add /tutorial/gift_receive — grant + receipt + idempotent re-claim

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SVSim.EmulatedEntrypoint/Models/Dtos/Requests/Gift/GiftReceiveRequest.cs

@@ -0,0 +1,16 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Requests.Gift;
+
+[MessagePackObject]
+public class GiftReceiveRequest : BaseRequest
+{
+    [JsonPropertyName("present_id_array")]
+    [Key("present_id_array")]
+    public List<string> PresentIdArray { get; set; } = new();
+
+    [JsonPropertyName("state")]
+    [Key("state")]
+    public int State { get; set; }
+}