Refactor OGG-FLAC streaming to support multi-client broadcast

Migrate from single-client direct OGG-FLAC sink to multi-client broadcast streaming sink.

- Replace DirectOggFlacHandle with OggFlacStreamHandle for multi-client support
- Update sink implementation to use StreamingOggFlacSink with proper backpressure
- Change connection model from 'connect()' to 'subscribe()'
- Adjust stream handling to support independent client streams
- Update stream endpoint to always respond with 200 chunked instead of range requests
- Add tracing for stream lifecycle events
- Reduce OGG channel capacity to strict backpressure (1)
- Add Drop implementation for stream cleanup
- Improve logging and error handling for concurrent access

This change enables multiple simultaneous clients to connect to the same audio stream without interfering with each other, while maintaining proper TCP backpressure and stream lifecycle management.

pmoaudio-ext/src/sinks/direct_ogg_flac_sink.rs

@@ -50,9 +50,9 @@ pub const DIRECT_OGG_FLAC_SAMPLE_RATE: u32 = 96_000;
 pub const DIRECT_OGG_FLAC_CHANNELS: u8 = 2;
 pub const DIRECT_OGG_FLAC_BITS_PER_SAMPLE: u8 = 24;
 
-/// Capacité du canal OGG → HTTP (en chunks de ~8 KB).
-/// Fournit un petit buffer sans casser la backpressure TCP.
-const OGG_CHANNEL_CAPACITY: usize = 8;
+/// Capacité du canal OGG → HTTP.
+/// Capacité 1 : backpressure stricte, l'encodeur ne produit pas en avance.
+const OGG_CHANNEL_CAPACITY: usize = 1;
 
 // ─── Types partagés ───────────────────────────────────────────────────────────
 
@@ -79,7 +79,7 @@ impl DirectOggFlacHandle {
     /// Retourne le stream OGG-FLAC pour le handler HTTP.
     /// Lance le premier encodeur au premier appel.
     pub fn get_stream(&self) -> DirectOggFlacStream {
-        debug!("DirectOggFlacHandle::get_stream()");
+        tracing::info!(target: "pmoaudio_ext::stream_connect", "get_stream() called — new HTTP client connecting");
         self.client_notify.notify_one();
         DirectOggFlacStream {
             ogg_rx: self.ogg_rx.clone(),
@@ -100,6 +100,12 @@ pub struct DirectOggFlacStream {
     buffer: VecDeque<u8>,
 }
 
+impl Drop for DirectOggFlacStream {
+    fn drop(&mut self) {
+        tracing::info!(target: "pmoaudio_ext::stream_connect", "DirectOggFlacStream dropped — HTTP client disconnected");
+    }
+}
+
 impl AsyncRead for DirectOggFlacStream {
     fn poll_read(
         mut self: Pin<&mut Self>,
@@ -118,6 +124,7 @@ impl AsyncRead for DirectOggFlacStream {
         let mut guard = match self.ogg_rx.try_lock() {
             Ok(g) => g,
             Err(_) => {
+                tracing::warn!(target: "pmoaudio_ext::stream_connect", "DirectOggFlacStream: try_lock() FAILED — concurrent access detected!");
                 cx.waker().wake_by_ref();
                 return Poll::Pending;
             }
@@ -126,6 +133,7 @@ impl AsyncRead for DirectOggFlacStream {
         match guard.poll_recv(cx) {
             Poll::Ready(Some(bytes)) => {
                 drop(guard);
+                tracing::info!(target: "pmoaudio_ext::stream_connect", "DirectOggFlacStream: sending {} bytes to HTTP client", bytes.len());
                 let to_copy = bytes.len().min(buf.remaining());
                 buf.put_slice(&bytes[..to_copy]);
                 if to_copy < bytes.len() {
@@ -133,7 +141,10 @@ impl AsyncRead for DirectOggFlacStream {
                 }
                 Poll::Ready(Ok(()))
             }
-            Poll::Ready(None) => Poll::Ready(Ok(())), // EOF
+            Poll::Ready(None) => {
+                tracing::info!(target: "pmoaudio_ext::stream_connect", "DirectOggFlacStream: ogg_rx closed → EOF sent to HTTP client");
+                Poll::Ready(Ok(()))
+            }
             Poll::Pending => Poll::Pending,
         }
     }