Re-use channel Uplink / Downlink for UDP controls

[thebentern]

For consideration

[Copilot]

Pull Request Overview

This PR adds channel-specific uplink and downlink control for UDP multicast communication by leveraging the existing channel configuration settings.

Key changes:

• Adds channel validation for both UDP uplink and downlink operations
• Modifies the onSend method signature to include channel index parameter
• Updates Router.cpp to pass channel information to UDP handler

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/mesh/udp/UdpMulticastHandler.h	Adds channel downlink/uplink validation and updates onSend method signature
src/mesh/Router.cpp	Updates UDP handler calls to pass channel index and reorganizes UDP handling logic

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[jp-bennett]

Only thing to consider is whether we would eventually want to control the UDP uplink separately from the MQTT.

[thebentern]

Agreed. I think in the long term we can split this control out into it's own levers

Only thing to consider is whether we would eventually want to control the UDP uplink separately from the MQTT.

[thebentern]

@GUVWAF added the default key fallback to this one

[GUVWAF]

isFromUs(p) is here still.

[GUVWAF]

Maybe instead of this bool we can use an int8_t to store the channel index where uplink is enabled, and -1 if none was found such that we can eliminate the same loop hereafter.