The MQTT settings dialog already has an Internal AetherSDR Topics section in the Subscriptions tab documenting topics AetherSDR subscribes to automatically. The Publish Buttons tab has no equivalent — leaving aethersdr/cw/decode (published for every decoded CW character since #3216) undiscoverable without reading source.

Proposed change: Add a read-only Internal AetherSDR Topics group box at the bottom of the Publish Buttons tab, mirroring the Subscriptions tab layout, showing:

• Topic: aethersdr/cw/decode
• Payload: {"text":"K","freq":14.025,"rx":true}
• rx: true = received CW, false = transmitted (sidetone)

Label text is selectable for copy-paste into subscriber configs.

Implementation notes:

• Mirror the internalGroup / internalText pattern already used in the Subscriptions tab (MqttSettingsDialog.cpp ~line 166)
• Add internalMqttPublishTopics() to MqttSettings.h/.cpp alongside the existing internalMqttSubscriptionTopics()
• UI-only; no behavior change

Files: src/core/MqttSettings.h, src/core/MqttSettings.cpp, src/gui/MqttSettingsDialog.cpp

Branch: feat/mqtt-publish-info-panel (implementation ready for review)