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

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

@@ -180,7 +180,7 @@ public class StoreAndForwardStorage
     /// Gets all messages that are due for retry (Pending status, last attempt older than retry interval).
     /// </summary>
     /// <returns>A task that resolves to the list of messages due for retry, ordered by creation time ascending.</returns>
-    public async Task<List<StoreAndForwardMessage>> GetMessagesForRetryAsync()
+    public async Task<List<StoreAndForwardMessage>> GetMessagesForRetryAsync(int limit = 0)
     {
         await using var connection = new SqliteConnection(_connectionString);
         await connection.OpenAsync();
@@ -197,6 +197,13 @@ public class StoreAndForwardStorage
                    OR (julianday('now') - julianday(last_attempt_at)) * 86400000 >= retry_interval_ms)
             ORDER BY created_at ASC";
 
+        // Bound the sweep batch (oldest-first). 0 = unlimited (legacy).
+        if (limit > 0)
+        {
+            cmd.CommandText += "\n            LIMIT @limit";
+            cmd.Parameters.AddWithValue("@limit", limit);
+        }
+
         cmd.Parameters.AddWithValue("@pending", (int)StoreAndForwardMessageStatus.Pending);
 
         return await ReadMessagesAsync(cmd);