fix: parse negative file sizes and fix for FTP 425 error on data connection

[frarcos]

This pull request addresses two specific issues related to FTP server interactions:

1. File Size Parsing Issue:

   • Some FTP servers return a file size of (-1) for certain files, which was not properly handled by the existing code.
   • The parsing regex has been updated to correctly interpret these negative file sizes, ensuring that such files are processed without errors.

2. FTP 425 Error on Data Connection:

   • The FTP 425 error occurs when the server fails to establish a data connection. After the PSV command, certain FTP servers require that the data connection is opened before any other commands are executed.
   • The directoryContent, download, and upload commands have been modified to respect this requirement. Now, these commands ensure that the data connection is properly established before proceeding, which prevents the FTP 425 error.