BackupSectionState
data class BackupSectionState(val identity: BackupLaneState, val dust: BackupLaneState, val appData: BackupLaneState?)
appData null → the App data lane is omitted. The wallet panel always provides a value (an informational "None yet" empty state when nothing has been saved) so users discover the capability; null stays available for hosts that genuinely have no app-data concept.