Mark the backup-now test as done in the plan

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/plans/guest-tui-mvp.md

@@ -344,5 +344,5 @@ Observed CLI behaviour (cv4pve-cli 2.4.0, all read-only probes):
 - [x] Tests (cli + UI contract) - red first.
 - [x] Implementation - suite green, ruff clean, README keys `i` / `b`.
 - [x] Read-only live check: open InfoScreen for CT 104 and VM 108, data shown.
-- [ ] User tests "Backup now" on CT 104.
+- [x] User tests "Backup now" on CT 104 (`debian (manual)`, 2026-11-02 21:09).
 - [ ] Push `feat/guest-info`, merge to `main` (user-approved after the test).