Enables the desktop share audio flow on Linux within Calls UI and plumbing.
- calls_call: add withAudio parameter to toggleScreenSharing, track
_screenWithAudio flag, create/destroy SystemAudioCapture when sharing
starts with audio, and clean it up in destroyController.
- calls_panel / calls_group_panel: use LoopbackAudioCaptureSupported()
to report audio support on all platforms; show a GenericBox with audio
toggle when a unique desktop capture source is available (PipeWire),
then start sharing with the chosen audio setting.
Depends on desktop-app/lib_webrtc#22
Closes#26642
paterkleomenis
f8fc9956d0