MeshBeaconConfigScreen

Editor for ModuleConfig.MeshBeaconConfig (design#140, Android issue #6931). Reads via AdminMessage.getModuleConfigRequest(MESHBEACON_CONFIG) and writes via AdminMessage.setModuleConfig. Flag edits are read-modify-write so unknown bits survive.

The region and offered/transmit preset are never user-chosen here: the radio's own LoRa region and configured preset are always stamped in on save (stampBeaconConfigForSave), so the beacon can never transmit region or preset information the radio itself does not use. broadcast_offer_* is the invitation payload content shown to listeners (what channel/preset they could join); the repeated broadcast_targets list (BroadcastTargetsCard) is the separate, only, TX destination list -- which radio settings the beacon packet itself is actually transmitted on. Firmware sends one beacon on the node's running preset and primary channel when this list is empty (MeshBeaconModule.cpp::sendBeacon), so the editor seeds and floors the list at one row (seedBeaconTargets, removeBeaconTarget) rather than ever showing zero rows -- design#140 behavior 6 keeps that implicit default visible and editable instead of hidden.