NODEINFO_APP is the better / authoritative source for a nodes primary channel.
MAP_REPORT_APP packets can arrive on a different MQTT uplink channel and
are unconditionally overwriting the channel set by NODEINFO, causing
nodes to appear on the wrong channel in the map and channel filters.
now MAP_REPORT_APP only sets Node.channel when it is not (yetw) known,
making it a fallback rather than an override.
