Initial toni-sync CLI: sync local playlist folders to Kreativ-Tonies

- Config commands (config add/list/remove) to map local audio folders
  to Kreativ-Tonies via TonieCloud household/tonie ids
- tonies list command to look up household/tonie ids
- sync command: diff-based upload of new tracks, pruning of removed
  chapters, and reordering to match local file order (via tonie-api)
- Credentials resolved via env vars/CLI flags/prompt, never stored
- Unit tests for config persistence and sync planning/apply logic

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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