OTA: quiet the audio sources during a firmware upload

An upload during an active Spotify session crawled (~10 kB/s, 197 s)
and ended in a reset (seen twice). Workaround:
- aes67_ota_on_update(cb): cb(true) right before an accepted upload
  writes flash, cb(false) if it then fails.
- The player pauses Spotify (spotify_pause -> SpircHandler::setPause, the
  app follows) and suspends HLS fetching (hls_suspend); resumed if the
  upload fails. AES67 TX keeps running (silence).
- Verified: upload during Spotify playback paused the session and
  installed in 25.8 s (normal for 2 MB), clean reboot and self-test.
  Root cause still open (noted in CLAUDE.md with the other cspot items).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

components/spotify/include/spotify.h

@@ -1,6 +1,7 @@
 // Spotify Connect (cspot). Project code; GPL-3.0 through cspot.
 #pragma once
 
+#include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ -24,6 +25,8 @@ typedef void (*spotify_event_cb_t)(spotify_event_t ev, int value);
 // Registers the zeroconf endpoints (/spotify_info) and, when source.mode is spotify/auto and the
 // client credentials are set, advertises the device and starts the session task.
 esp_err_t spotify_init(spotify_pcm_cb_t pcm, spotify_event_cb_t event);
+// Pause/resume the running session (the Spotify app follows). No-op without a session.
+void spotify_pause(bool pause);
 // Current state for status.spotify_state.
 const char *spotify_state(void);