feat(item-acquire-history): controller + DTOs

Add ItemAcquireHistoryController (POST /item_acquire_history/info) with its
three DTOs and two integration tests (ordering + empty-viewer). The endpoint
reads ViewerAcquireHistory rows written by InventoryTransaction.CommitAsync,
ordered newest-first, capped at 300. Tests access doc.RootElement.histories
directly (no envelope wrapper in the test path — middleware skips non-UnityPlayer UA).

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

SVSim.EmulatedEntrypoint/Models/Dtos/ItemAcquireHistory/ItemAcquireHistoryEntryDto.cs

@@ -0,0 +1,36 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.ItemAcquireHistory;
+
+/// <summary>
+/// One row in the <c>/item_acquire_history/info</c> response. All numeric fields ship as
+/// decimal strings to match the prod capture.
+/// </summary>
+[MessagePackObject]
+public sealed class ItemAcquireHistoryEntryDto
+{
+    [JsonPropertyName("reward_type")]
+    [Key("reward_type")]
+    public string RewardType { get; set; } = "0";
+
+    [JsonPropertyName("reward_detail_id")]
+    [Key("reward_detail_id")]
+    public string RewardDetailId { get; set; } = "0";
+
+    [JsonPropertyName("reward_count")]
+    [Key("reward_count")]
+    public string RewardCount { get; set; } = "0";
+
+    [JsonPropertyName("acquire_type")]
+    [Key("acquire_type")]
+    public string AcquireType { get; set; } = "0";
+
+    [JsonPropertyName("acquire_time")]
+    [Key("acquire_time")]
+    public string AcquireTime { get; set; } = string.Empty;
+
+    [JsonPropertyName("message")]
+    [Key("message")]
+    public string Message { get; set; } = string.Empty;
+}

SVSim.EmulatedEntrypoint/Models/Dtos/ItemAcquireHistory/ItemAcquireHistoryInfoRequest.cs

@@ -0,0 +1,12 @@
+using MessagePack;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.ItemAcquireHistory;
+
+/// <summary>
+/// Empty request body. The endpoint takes no parameters; this DTO exists so model binding
+/// resolves the envelope correctly.
+/// </summary>
+[MessagePackObject(true)]
+public sealed class ItemAcquireHistoryInfoRequest
+{
+}

SVSim.EmulatedEntrypoint/Models/Dtos/ItemAcquireHistory/ItemAcquireHistoryInfoResponse.cs

@@ -0,0 +1,12 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.ItemAcquireHistory;
+
+[MessagePackObject]
+public sealed class ItemAcquireHistoryInfoResponse
+{
+    [JsonPropertyName("histories")]
+    [Key("histories")]
+    public List<ItemAcquireHistoryEntryDto> Histories { get; set; } = new();
+}