feat: add --backup-converted flag to keep .orig backups

internal/protocol/http/client.go

@@ -403,6 +403,7 @@ func (c *Client) downloadMirror(ctx context.Context, req *core.DownloadRequest)
 		ConvertLinks:    c.config.Recursive.ConvertLinks,
 		DownloadAssets:  c.config.Recursive.MirrorAssets,
 		PruneEmpty:      true,
+		BackupConverted: c.config.Recursive.BackupConverted,
 		RestrictFiles:   true,
 		Timeout:         c.config.Transport.Timeout,
 		RespectRobots:   c.config.Recursive.RespectRobots,

internal/protocol/http/config_types.go

@@ -84,10 +84,11 @@ type RecursiveConfig struct {
 	DryRun    bool
 
 	// Mirror mode
-	Mirror        bool
-	MirrorAssets  bool
-	ConvertLinks  bool
-	RespectRobots bool
+	Mirror          bool
+	MirrorAssets    bool
+	ConvertLinks    bool
+	BackupConverted bool
+	RespectRobots   bool
 }
 
 // OutputConfig groups output, progress, and display settings.