models(card): MaxCopies constant on OwnedCardEntry

SVSim.Database/Models/OwnedCardEntry.cs

@@ -8,6 +8,13 @@ namespace SVSim.Database.Models;
 [Owned]
 public class OwnedCardEntry
 {
+    /// <summary>
+    /// Game rule: a viewer may own at most this many copies of a single card. Mirrors the
+    /// client constant <c>CardMake.CAN_CREATE_MAX = 3</c>. Used by <c>/card/create</c> to
+    /// reject batches that would exceed the cap.
+    /// </summary>
+    public const int MaxCopies = 3;
+
     public ShadowverseCardEntry Card { get; set; } = new ShadowverseCardEntry();
     public int Count { get; set; }
     public bool IsProtected { get; set; }