Department views for kitchen/bar tablets

[vekexasia]

Follow-up to #15/#18.

Each order destination (department) should have a dedicated full-screen view suitable for a tablet mounted in the kitchen/bar:

• Large cards, touch-friendly mark-done, auto-refresh.
• Scoped to a single department (the current kitchen board has per-department tabs, but it lives inside the admin UI and is not tablet-friendly).
• Access model TBD: likely the staff-link mechanism from Waiter mode: staff floor view with table sessions and one-use staff links #15 (one-use link per device) rather than admin login on a shared tablet.

Not scheduled yet — parked here so it doesn't get lost.