perf(store-and-forward): bound retry sweep with SweepBatchLimit (default 500) on the due-rows query

src/ZB.MOM.WW.ScadaBridge.StoreAndForward/StoreAndForwardOptions.cs

@@ -22,4 +22,11 @@ public class StoreAndForwardOptions
 
     /// <summary>Interval for the background retry timer sweep.</summary>
     public TimeSpan RetryTimerInterval { get; set; } = TimeSpan.FromSeconds(10);
+
+    /// <summary>
+    /// Maximum due rows loaded per retry sweep. Bounds sweep memory and duration
+    /// under backlog; the remainder is picked up on the next tick (10 s).
+    /// 0 = unlimited (legacy).
+    /// </summary>
+    public int SweepBatchLimit { get; set; } = 500;
 }