`drop-core` Add transfer speed and ETA to CLI progress output

[pushkarm029]

Currently, the CLI shows progress as percentage and bytes transferred, but doesn't display transfer speed or estimated time remaining. This would improve UX significantly for large file transfers.

Implementation considerations:

• Calculate speed using a rolling average over the last few seconds to smooth out fluctuations
• Format bytes in human-readable units (KB/s, MB/s, GB/s) based on magnitude
• Calculate ETA based on current transfer speed and remaining bytes

Additional improvements:

• Show instantaneous and average speeds
• Add option to toggle between detailed and simple progress display

more info: #101 (comment)