fix(sensor): stamp Last MQTT Received on multiSync events too

multiSync messages (H5043 leak-hub events) are genuine inbound MQTT
traffic but were dispatched before the freshness stamp, so a leak-only
install showed 'Last MQTT Received' as permanently unavailable. Move the
stamp above the message-type branch so any accepted device message counts
as transport activity.

Author: Tom Lasswell

custom_components/govee/api/mqtt.py

@@ -397,6 +397,11 @@ async def _handle_message(self, message: Any) -> None:
                 _LOGGER.debug("AWS IoT message missing device ID, ignoring")
                 return
 
+            # Any accepted inbound device message proves the MQTT transport is
+            # live — stamp freshness before branching on message type so leak
+            # events (multiSync) count as activity, not just state updates.
+            self._last_message_ts = datetime.now(timezone.utc)
+
             # Handle multiSync messages (leak sensor events)
             cmd = data.get("cmd")
             if cmd == "multiSync":
@@ -419,7 +424,6 @@ async def _handle_message(self, message: Any) -> None:
             )
 
             self._last_messages[device_id] = state
-            self._last_message_ts = datetime.now(timezone.utc)
 
             # Invoke callback with device ID and state dict
             try: