Mobile: live external audio input (USB) source selector

Expose the engine's live-input mode on the remote: an "Sorgente audio"
selector in the Audio tab lists the input devices the output reports and
switches between File/Playlist and a live USB capture (useInput); picking
File again stops the input. Grant the kiosk getUserMedia access with
--use-fake-ui-for-media-stream so device enumeration/labels work without a
prompt. Make reportDevices resilient (per-probe timeout, always report even
an empty list) so the UI gets feedback when no input is connected yet.

The Pi 5 has no audio input — a USB (line) sound card is required; visuals
react to the source while the audio stays on the mixer.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scripts/kiosk.sh

@@ -5,6 +5,7 @@ BIN="$(command -v chromium-browser || command -v chromium || echo chromium)"
 exec "$BIN" \
   --kiosk --noerrordialogs --disable-infobars --no-first-run \
   --autoplay-policy=no-user-gesture-required \
+  --use-fake-ui-for-media-stream \
   --disable-translate --disable-features=Translate \
   --check-for-update-interval=31536000 \
   --overscroll-history-navigation=0 \