Increase PCM buffer capacity from 8 to 256 to prevent encoding glitches

The small buffer (8) was causing the pump to block frequently when the FLAC
encoder was slow to consume data. This created micro-pauses in the PCM stream
that resulted in audible clicks in the encoded FLAC files.

With a larger buffer (256), the pump can continue sending data without blocking,
ensuring continuous audio flow to the encoder and eliminating the clicks.

pmoaudio-ext/src/sinks/flac_cache_sink.rs

@@ -435,7 +435,7 @@ impl FlacCacheSink {
         encoder_options: EncoderOptions,
         collection: Option<String>,
     ) -> Self {
-        let logic = FlacCacheSinkLogic::new(cache, covers, collection, encoder_options, 8);
+        let logic = FlacCacheSinkLogic::new(cache, covers, collection, encoder_options, 256);
         Self {
             inner: Node::new_with_input(logic, channel_size),
         }