docs: 以MQTT V2协议校正注册绑定说明

docs/architecture/02-device-bootstrap.md

@@ -60,9 +60,10 @@ response on `msg_id=012`:
 }
 ```
 
-The ICCID belongs to the later `msg_id=006` device-binding success receipt,
-not to this registration response. The registration response only establishes
-the device identity needed by the binding flow.
+The current V2.0 registration response does not carry an ICCID. Any ICCID
+addition belongs to the separate `msg_id=006` binding-response extension; the
+registration response only establishes the device identity needed by the
+binding flow.
 
 ## Data Model
 
@@ -101,6 +102,7 @@ serial_number: TQ_ZHWK000000002001
 
 ## Source Anchors
 
+- MQTT protocol V2.0: `talkingq-url/docs/mqtt协议_V2.0.txt`
 - Bootstrap handler: `talkingq-url/handlers/mqtt_handler.py`
 - Identity initializer: `talkingq-url/services/device_identity_initializer.py`
 - Import script: `talkingq-url/scripts/import_device_imei_mapping.py`