Lets the POS agent and the QR/app customer attach a free-text note to each
order line (e.g. "no tomato", "extra hot") that reaches the kitchen/bar.
- Backend already supported it (OrderItem.Notes persists; CreateOrderItemRequest
and OrderItemDto carry Notes; LiveOrderDto items include it) — this wires the UI.
- cart.store: add setNotes(menuItemId, notes); notes already travel in
getPendingLines and round-trip via hydrateFromOrder.
- POS pos-screen: a note input under each cart line.
- QR guest menu: a note input under each cart line (QrCartLine.note).
- KDS: render the note prominently under each item so kitchen/bar sees it.
- i18n: pos.itemNotePlaceholder + qrMenu.itemNote (fa/ar/en).
Note: notes are captured on items being added; editing a note on an
already-submitted line is out of scope (no pending delta to re-send).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>