harden qobuz and downloader reliability edge cases

internal/audio/convert/convert.go

@@ -72,6 +72,17 @@ func buildFFmpegArgs(inputPath, outputPath string, p profile, cfg config.Convers
 		"-c:a", p.codecLib,
 	}
 
+	if supportsAttachedPicture(p.ext) {
+		args = append(args,
+			"-map", "0:v:0?",
+			"-c:v", "mjpeg",
+			"-disposition:v:0", "attached_pic",
+		)
+		if p.ext == "mp3" {
+			args = append(args, "-id3v2_version", "3")
+		}
+	}
+
 	if p.lossless {
 		filter := buildLosslessFilter(cfg)
 		if filter != "" {
@@ -87,6 +98,15 @@ func buildFFmpegArgs(inputPath, outputPath string, p profile, cfg config.Convers
 	return args
 }
 
+func supportsAttachedPicture(ext string) bool {
+	switch strings.TrimPrefix(strings.ToLower(ext), ".") {
+	case "flac", "mp3", "m4a", "mp4":
+		return true
+	default:
+		return false
+	}
+}
+
 func buildLosslessFilter(cfg config.ConversionConfig) string {
 	parts := make([]string, 0, 2)
 	if cfg.SamplingRate > 0 {