refactor(inventory): share retention cap + invariant-culture date format

Introduce InventoryHistoryConfig.RetentionRowsPerViewer as the single
source of truth for the 300-row audit-log cap; InventoryTransaction
aliases it and ItemAcquireHistoryController.Take() references it
directly so the two sites cannot drift. Also adds CultureInfo.InvariantCulture
to the AcquireTime.ToString() call, matching every other WireDateFormat
site in the codebase.

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

SVSim.Database/Services/Inventory/InventoryHistoryConfig.cs

@@ -0,0 +1,15 @@
+namespace SVSim.Database.Services.Inventory;
+
+/// <summary>
+/// Shared knobs for the viewer-acquire-history audit log. The write-side prune cap
+/// (in <c>InventoryTransaction</c>) and the read-side page size (in
+/// <c>ItemAcquireHistoryController</c>) both reference these constants so they cannot drift.
+/// </summary>
+public static class InventoryHistoryConfig
+{
+    /// <summary>
+    /// Maximum rows kept per viewer. Older rows are pruned by
+    /// <c>InventoryTransaction.CommitAsync</c>; the read endpoint pages exactly this many.
+    /// </summary>
+    public const int RetentionRowsPerViewer = 300;
+}

SVSim.Database/Services/Inventory/InventoryTransaction.cs

@@ -9,7 +9,7 @@ namespace SVSim.Database.Services.Inventory;
 
 internal sealed class InventoryTransaction : IInventoryTransaction
 {
-    private const int AcquireHistoryRetention = 300;
+    private const int AcquireHistoryRetention = InventoryHistoryConfig.RetentionRowsPerViewer;
 
     private readonly SVSimDbContext _db;
     private readonly IDbContextTransaction _dbTx;