The two-way audio talkback loopback (RtspServer over listenZeroSingleClient)
only supports TCP interleaved transport. The talkback ffmpeg input was built
without -rtsp_transport, so ffmpeg attempts a UDP SETUP first and the loopback
responds 461 Unsupported Transport.
The equivalent webrtc talkback path (plugins/webrtc/src/session-control.ts)
has always specified -rtsp_transport tcp; the homekit path did not. Align it.
Before: talkback was silent and the log showed "method SETUP failed: 461
Unsupported Transport". After: the 461 is gone and talkback audio works.
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