docs: clarify kafka-only production channel

docs/module-data-flow.html

@@ -414,7 +414,7 @@ sequenceDiagram
   participant Dispatcher as Dispatcher
   participant Handler as Protocol Handler<br/>Mapper
   participant EventBus as DisruptorEventBus
-  participant MQ as sink-kafka<br/>Kafka Envelope
+  participant Kafka as sink-kafka<br/>Kafka Envelope
   participant Archive as sink-archive<br/>ArchiveStore
   participant History as vehicle-history-app
   participant TDengine as tdengine-history-store<br/>raw_frames + locations
@@ -430,12 +430,12 @@ sequenceDiagram
   Handler->>Handler: 协议字段映射为内部字段
   Dispatcher->>Handler: 绑定 rawArchiveKey / rawArchiveUri
   Handler->>EventBus: VehicleEvent(Realtime / Location / Alarm / Login ...)
-  EventBus->>MQ: 投递规整后的业务事件
-  MQ->>MQ: EnvelopeMapper 转 Protobuf
-  MQ->>History: Kafka event/raw topic，key=vin，单车有序
+  EventBus->>Kafka: 投递规整后的业务事件
+  Kafka->>Kafka: EnvelopeMapper 转 Protobuf
+  Kafka->>History: event/raw topic，key=vin，单车有序
   History->>TDengine: 写 raw_frames、locations 和 raw parsed JSON
   TDengine->>Consumer: 分页历史查询、原始帧追溯、位置查询
-  MQ->>Consumer: Redis 热状态、指标统计、告警工单等下游消费
+  Kafka->>Consumer: Redis 热状态、指标统计、告警工单等下游消费
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