feat: enable processing of large video files over 2GB

Update audio extraction to use file-based streaming
instead of in-memory buffers to support processing
video files larger than 2GB.

**Changes:**
- Modified `IAudioExtractor.ExtractMp3FromMp4Async()`
  to accept an output audio stream parameter instead
  of creating a MemoryStream internally
- Updated `AudioExtractor` to write directly to the
  provided audio stream, eliminating the need to load
  entire video into memory
- Enhanced `FFMpegService` to detect FileStream inputs
  and use direct file-to-file processing when possible,
  falling back to pipe-based streaming for other stream types
- Refactored `DefaultCommand` to create output directory
  and audio file stream before extraction, enabling direct
  file-based audio extraction
- Updated all unit and integration tests to accommodate the
  new audio stream parameter

This change prevents `OutOfMemoryException` errors when processing
large video files by streaming data directly to disk rather than
buffering in memory. Additionally, it removes the possibility of
overflowing the 2GB size limit that `MemoryStream` has, which
would result in `IOException` errors when trying to write or
copy to it.

src/StreamShorts.Library/Media/FFMpegService.cs

@@ -12,14 +12,17 @@ internal sealed class FFMpegService : IVideoService
 {
   public async Task<bool> ExtractAudioFromVideoAsync(Stream video, Stream audio)
   {
-    return await FFMpegArguments
-      .FromPipeInput(new StreamPipeSource(video))
-      .OutputToPipe(
-        new StreamPipeSink(audio),
-        static o => o.DisableChannel(Channel.Video).ForceFormat("mp3")
-      )
-      .ProcessAsynchronously()
-      .ConfigureAwait(false);
+    var inputArguments = video is FileStream videoFileStream
+      ? FFMpegArguments.FromFileInput(videoFileStream.Name)
+      : FFMpegArguments.FromPipeInput(new StreamPipeSource(video));
+
+    Action<FFMpegArgumentOptions> arguments = static o => o.DisableChannel(Channel.Video).ForceFormat("mp3");
+
+    var processor = audio is FileStream audioFileStream
+      ? inputArguments.OutputToFile(audioFileStream.Name, addArguments: arguments)
+      : inputArguments.OutputToPipe(new StreamPipeSink(audio), addArguments: arguments);
+    
+    return await processor.ProcessAsynchronously().ConfigureAwait(false);
   }
 
   public async Task CreateClipFromVideoAsync(