- Add privilege escalation at startup (pkexec if not root)
- Remove all sudo password handling (echo password | sudo -S)
- Remove show_sudo_dialog and current_sudo_password_
- Remove --sudo-password CLI option
- All rsync/restore operations run directly as root
- format_size: use GB as default unit for large files
- Remove [cmd] log leaking sudo password
- Simplify snapshot_manager: no sudo_password parameter
- Simplify rsync_manager: no sudo_password parameter
- Fix gtk_box_pack on GtkMenuBar (was treated as GtkBox): build_toolbar() now returns widget instead of packing into toolbar_ member
- Fix markup error: </big></big> -> </big></b> in backup window header
- Fix segfault: validate tag name against TextBuffer tag table before use
- Add missing 'cmd' tag to live log buffer
- Add NULL sentinel to gtk_text_buffer_insert_with_tags_by_name calls
- Add estimate_backup_size() using du -sb before rsync starts
- Parse transfer speed from rsync output (KB/s, MB/s, GB/s)
- Calculate remaining time based on speed and remaining bytes
- Show estimated time remaining and size progress in UI
- Add format_time_remaining() for human-readable time display
- New UI elements: backup_time_label_ and backup_size_label_
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