feat: add diagnostic logging for audio input and frame processing

- Log audio input details (type, source, sample rate, channels) when opening
- Log first PCM frame metadata (size, samples, bytes per frame) for debugging
- Log first LC3 encoded frame size to verify encoding pipeline

src/auracast/multicast.py

@@ -597,6 +597,9 @@ class Streamer():
                 for attempt in range(1, max_attempts + 1):
                     try:
                         pcm_format = await audio_input.open()
+                        logging.info(
+                            f"Opened audio input: {type(audio_input).__name__} src={audio_source} sr={pcm_format.sample_rate} ch={pcm_format.channels}"
+                        )
                         break  # success
                     except _sd.PortAudioError as err:
                         # -9985 == paDeviceUnavailable
@@ -720,6 +723,12 @@ class Streamer():
                     # Read the frame we need for encoding
                     pcm_frame = await anext(frames_gen, None)
 
+                    if big.get('logged_first_frame') is not True:
+                        logging.info(
+                            f"First PCM frame bytes={0 if pcm_frame is None else len(pcm_frame)} | lc3_frame_samples={big['lc3_frame_samples']} | bytes_per_frame={big['lc3_bytes_per_frame']}"
+                        )
+                        big['logged_first_frame'] = True
+
                     if pcm_frame is None: # Not all streams may stop at the same time
                         stream_finished[i] = True
                         continue
@@ -808,6 +817,13 @@ class Streamer():
                         pcm_frame, num_bytes=big['lc3_bytes_per_frame'], bit_depth=big['pcm_bit_depth']
                     )
 
+                if big.get('logged_first_lc3') is not True:
+                    try:
+                        logging.info(f"First LC3 frame size={len(lc3_frame)} bytes")
+                    except Exception:
+                        pass
+                    big['logged_first_lc3'] = True
+
                 await big['iso_queue'].write(lc3_frame)
                 frame_count += 1
                 # Increment guard counter (tracks frames since last discard)