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/Controllers/ItemAcquireHistoryController.cs

@@ -0,0 +1,46 @@
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+using SVSim.Database;
+using SVSim.EmulatedEntrypoint.Models.Dtos.ItemAcquireHistory;
+
+namespace SVSim.EmulatedEntrypoint.Controllers;
+
+[Route("item_acquire_history")]
+public sealed class ItemAcquireHistoryController : SVSimController
+{
+    private const string WireDateFormat = "yyyy-MM-dd HH:mm:ss";
+    private const int PageSize = 300;
+
+    private readonly SVSimDbContext _db;
+
+    public ItemAcquireHistoryController(SVSimDbContext db) => _db = db;
+
+    [HttpPost("info")]
+    public async Task<ActionResult<ItemAcquireHistoryInfoResponse>> Info(
+        [FromBody] ItemAcquireHistoryInfoRequest _,
+        CancellationToken ct)
+    {
+        if (!TryGetViewerId(out var viewerId)) return Unauthorized();
+
+        var rows = await _db.ViewerAcquireHistory
+            .Where(h => h.ViewerId == viewerId)
+            .OrderByDescending(h => h.AcquireTime)
+            .ThenByDescending(h => h.Id)
+            .Take(PageSize)
+            .AsNoTracking()
+            .ToListAsync(ct);
+
+        return new ItemAcquireHistoryInfoResponse
+        {
+            Histories = rows.Select(h => new ItemAcquireHistoryEntryDto
+            {
+                RewardType = h.RewardType.ToString(),
+                RewardDetailId = h.RewardDetailId.ToString(),
+                RewardCount = h.RewardCount.ToString(),
+                AcquireType = h.AcquireType.ToString(),
+                AcquireTime = h.AcquireTime.ToString(WireDateFormat),
+                Message = h.Message,
+            }).ToList(),
+        };
+    }
+}