Limit active listings to 10

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/Decentralized.Domain/BmSales.cs

@@ -53,13 +53,15 @@ namespace Decentralized.Domain
             return Math.Min(Tuning.BmVolumeTaintMax, v / Tuning.BmVolumeRef * Tuning.BmVolumeTaintMax);
         }
 
+        public int ActiveListings => Sales.Count(x => x.State == SaleState.Listed);
+
         public static int ListPriceOf(long refValue, double m) => (int)Math.Max(1, Math.Round(refValue * m));
         public static int ListFee(int listPrice) => (int)Math.Ceiling(listPrice * Tuning.BmListFee);
 
         /// <summary>上架：交付一件货，收上架费（付给 feeAsset 币，污点与成本按比例带走）。倍率超出范围、平台关闭或余额不足返回 null。</summary>
         public BmSale List(string item, string model, string fakeOf, double health, long refValue, double m, Wallet w, string feeAsset, int day, Func<string, double> price)
         {
-            if (m < Tuning.BmSellMin - 1e-9 || m > Tuning.BmSellMax + 1e-9 || refValue <= 0 || Closed(day) || feeAsset == Assets.CRC) return null;
+            if (m < Tuning.BmSellMin - 1e-9 || m > Tuning.BmSellMax + 1e-9 || refValue <= 0 || Closed(day) || feeAsset == Assets.CRC || ActiveListings >= Tuning.BmMaxListings) return null;
             int listPrice = ListPriceOf(refValue, m);
             double p = price(feeAsset);
             if (p <= 0) return null;