Add operation progress overlay to TUI and wire pwr tui subcommand in CLI

Implement an OperationOverlay screen for the ratatui-based TUI that renders
a centered modal dialog with a progress gauge, transfer statistics, and a
cancel prompt during archive and restore operations. The overlay displays
the operation name and project name in the title bar, a cyan progress
gauge driven by the bytes_done/bytes_total ratio, a statistics line
showing human-readable byte counts with percentage, and a status line that
changes between ‘Press Esc to cancel’ during transfer, ‘Transfer complete’
on success, and red error text on failure. The format_size helper converts
byte counts to GB/MB/KB/B with one decimal place. The handle_input method
maps Escape to cancellation and Enter to dismissal after completion.

Wire the pwr tui subcommand into the CLI behind the tui feature flag. The
Commands enum gains a Tui variant gated by #[cfg(feature = “tui”)], the
dispatch match arm calls cmd_tui(), and the tui module is conditionally
compiled. Building without –features tui produces a CLI-only binary;
building with the flag includes the ratatui and crossterm dependencies and
the tui module, enabling pwr tui to launch the interactive interface.