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/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();
+}