Spotify follows source mode, name and credentials live

- spotify_init() sets up the logger, zeroconf routes and session task
  once; spotify_apply() (at boot and on every source save) enables or
  disables: enabled = mode spotify/auto + credentials. Disable removes
  the mDNS entry, zeroconf answers 404 and a running session ends
  (loop exits within 200 ms, SpircHandler::disconnect stops the queue
  and player tasks). A new device name ends the session and
  re-advertises. The login blob is swapped under a mutex.
- Verified: hls/spotify/rename switch the mDNS entry and /spotify_info
  (404/200) live; switching to hls during Spotify playback ended the
  session in < 2 s, HLS played after ~5 s, internal heap 221 -> 365 KB
  (cspot frees everything).
- CLAUDE.md: OTA-with-session findings (intermittent, flash-write stalls
  seen as TX resyncs during uploads), serial-port reset caveat.

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

components/spotify/include/spotify.h

@@ -22,9 +22,12 @@ typedef enum {
 typedef size_t (*spotify_pcm_cb_t)(const int16_t *pcm, size_t frames);
 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.
+// Registers the zeroconf endpoints (/spotify_info), starts the session task and applies the config.
 esp_err_t spotify_init(spotify_pcm_cb_t pcm, spotify_event_cb_t event);
+// Re-read the "source" config: enabled (advertised, sessions accepted) when mode is spotify/auto and
+// the client credentials are set; otherwise not advertised and a running session is ended.
+// A new device name ends the session and re-advertises.
+void spotify_apply(void);
 // 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.