Show progress bar with transfer speed during file move/copy operations

Is your feature request related to a problem? Please describe.

When moving or copying files between directories (especially large files or batches), the UI only shows a generic "Operation in progress, please wait..." dialog with no indication of progress, transfer speed, or estimated time remaining. I often move large media folders (10–100+ GB) between datasets on my NAS, and with the current implementation there's no way to tell whether the operation is actually progressing or if it has hung — especially for moves across different filesystems or mount points where the operation involves an actual copy rather than a quick rename.

Describe the solution you'd like A progress dialog that displays:

• Overall progress percentage and progress bar
• Current transfer speed (MB/s)
• Estimated time remaining (ETA)
• Current file being processed (when moving multiple files)
• Number of files completed vs total (e.g., "3 of 15 files")

Ideally with the ability to minimize the dialog and continue using the UI while the operation runs in the background.

Describe alternatives you've considered

• Falling back to SSH and using mv/rsync for large transfers — works, but defeats the purpose of having a web file manager.
• Using a separate terminal session to monitor disk I/O with iotop to confirm the operation is still running — clunky workaround.

Additional context Most modern file managers (Dolphin, Nautilus, Windows Explorer, macOS Finder) provide this kind of feedback during file operations. Adding it would bring FileBrowser Quantum closer to feature parity with native desktop file managers and make it much more comfortable for managing large media libraries. Screenshot of the current "operation in progress" dialog attached for reference.

Thanks for the great work on this project!