Step 7.4: HLS audio on AES67 (44.1 -> 48 kHz into the ring)

- decoder: s16 PCM -> stereo int32 -> esp_ae_rate_cvt 44.1 -> 48 kHz
  (32-bit, complexity 3; bypassed at 48 kHz; mono duplicated) -> ring.
  esp_audio_effects pinned to ~1.3.0 (1.4+ needs P4 rev >= 3).
- hls: each segment is downloaded completely into PSRAM (max 4 MB), then
  decoded; the connection is not held open while the decoder waits for
  ring space at playback speed.
- player: player_write() blocks while the ring is full and gives up when
  the source changes; the temporary 440 Hz producer is removed.
- Verified with Triple J Hottest: 441344 -> 480375 frames (10.008 s) and
  440320 -> 479260 (9.985 s) per segment; RTP 15000 packets, 0 gaps,
  peak -10 dBFS / RMS -22 dBFS; ring ~4.0 s, 0 underruns over ~50 s;
  heap 422 KB, PSRAM 27.5 MB free.

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

main/player.h

@@ -1,9 +1,14 @@
 // Project player: picks the audio source for AES67 TX (test tone, silence, HLS, Spotify).
 #pragma once
 
+#include <stddef.h>
+#include <stdint.h>
+
 #include "cJSON.h"
 #include "esp_err.h"
 
 esp_err_t player_init(void);
 // Apply the "source" config group (mode etc.).
 void player_apply(const cJSON *source);
+// Source side: write 48 kHz stereo int32 frames, blocking while the ring is full.
+size_t player_write(const int32_t *frames, size_t n);