refactor: frame converter and mp4 track improvements

- Refactor frame converter implementation
- Update mp4 track to use ICodex
- General refactoring and code improvements

🤖 Generated with [Claude Code](https://claude.ai/code)

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

example/test/main.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+
+	"m7s.live/v5"
+	_ "m7s.live/v5/plugin/cascade"
+
+	_ "m7s.live/v5/plugin/debug"
+	_ "m7s.live/v5/plugin/flv"
+	_ "m7s.live/v5/plugin/gb28181"
+	_ "m7s.live/v5/plugin/hls"
+	_ "m7s.live/v5/plugin/logrotate"
+	_ "m7s.live/v5/plugin/mp4"
+	_ "m7s.live/v5/plugin/onvif"
+	_ "m7s.live/v5/plugin/preview"
+	_ "m7s.live/v5/plugin/rtmp"
+	_ "m7s.live/v5/plugin/rtp"
+	_ "m7s.live/v5/plugin/rtsp"
+	_ "m7s.live/v5/plugin/sei"
+	_ "m7s.live/v5/plugin/snap"
+	_ "m7s.live/v5/plugin/srt"
+	_ "m7s.live/v5/plugin/stress"
+	_ "m7s.live/v5/plugin/test"
+	_ "m7s.live/v5/plugin/transcode"
+	_ "m7s.live/v5/plugin/webrtc"
+	_ "m7s.live/v5/plugin/webtransport"
+)
+
+func main() {
+	conf := flag.String("c", "config.yaml", "config file")
+	flag.Parse()
+	// ctx, _ := context.WithDeadline(context.Background(), time.Now().Add(time.Second*100))
+	err := m7s.Run(context.Background(), *conf)
+	fmt.Println(err)
+}