fix(concurrency,durability): address Opus review critical findings

- create_queue: SaveQueue under per-queue lock, not global SyncQueues.Lock
  (fixes fatal concurrent map iteration/write on idempotent CreateQueue of existing FIFO queue)
- delete_message_batch: reject empty ReceiptHandle (JSON protocol bypass deleted all unreceived msgs)
- send_message/send_message_batch: register dedupId only after successful persist
  (retry with same dedupId no longer returns 200 without persisting)
- memory_guard: global HeapAlloc guard (SHARED_SQS_MAX_HEAP_MB, 0=off) in send paths

app/gosqs/delete_message_batch.go

@@ -54,6 +54,12 @@ func DeleteMessageBatchV1(req *http.Request) (int, interfaces.AbstractResponseBo
 			return utils.CreateErrorResponseV1("BatchEntryIdsNotDistinct", true)
 		}
 		ids[v.Id] = true
+		// Пустой ReceiptHandle опасен: в JSON-протоколе (x-amz-json-1.0) он не
+		// отсекается парсером и совпадает с ReceiptHandle НЕвыданных сообщений (""),
+		// что удаляло бы все такие сообщения очереди одним запросом.
+		if v.ReceiptHandle == "" {
+			return utils.CreateErrorResponseV1("InvalidParameterValue", true)
+		}
 	}
 
 	queue := models.SyncQueues.GetLocked(key)