Add `restore` command to undo a dedupe

[jaimalleshk]

Move files back out of the _duplicates/ quarantine folder to their original location, so a dedupe can be reversed.

Why: builds trust in the dedupe workflow; the quarantine is reversible by design but there's no command for it yet.

Scope

• tidysync restore <remote> [--folder ...] [--apply] (report-only by default).
• Read _duplicates/<original/path> entries and moveto each back to <original/path>.
• Skip/flag if a file already exists at the destination (don't clobber).
• Add a menu option and an offline test (stub rclone).

Code: src/tidysync/dedupe.py, src/tidysync/rclone.py (moveto), cli.py, interactive.py.