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>

main/hls.c

@@ -36,6 +36,12 @@ static media_pl_t *s_pl;            // parsed media playlist (PSRAM)
 static char s_url[URL_MAX];         // configured URL
 static char s_media_url[URL_MAX];
 static uint8_t *s_seg;              // current segment (PSRAM)
+static volatile bool s_suspended;
+
+void hls_suspend(bool suspend)
+{
+    s_suspended = suspend;
+}
 
 // hls_url when source.mode needs HLS, else "".
 static void wanted_url(char *out, size_t n)
@@ -50,6 +56,9 @@ static void wanted_url(char *out, size_t n)
 
 static bool still_wanted(void)
 {
+    if (s_suspended) {
+        return false;
+    }
     char u[URL_MAX];
     wanted_url(u, sizeof(u));
     return strcmp(u, s_url) == 0;
@@ -237,7 +246,7 @@ static void hls_task(void *arg)
 {
     while (1) {
         wanted_url(s_url, sizeof(s_url));
-        if (!s_url[0]) {
+        if (!s_url[0] || s_suspended) {
             vTaskDelay(pdMS_TO_TICKS(1000));
             continue;
         }