kitchen display system-kds enhancement

New feature 1: countdown timer for orders approaching time slot

a countdown timer will appear for any order that is within a defined number of minutes from its scheduled time slot.

configuration:

1. setting name: show countdown for orders approaching slot
2. function: when set to a value greater than 0, the countdown timer becomes visible for orders within the specified timeframe.

visual behavior:

1. red blinking background when order is within the countdown window.
2. yellow background with a "timeout" label once the scheduled time passes.
3. blue background with "preorder" label if order is outside the countdown window.

New feature 2: elapsed time since order placement

shows how long it has been since each order was placed, helping kitchen staff prioritize older orders.

configuration:

1. setting name: show elapsed time for orders after x minutes
2. function: when a value is configured, elapsed time (e.g., "12 min ago") will appear only for orders that exceed that threshold.

display behavior:

1. updates in real time every minute.
2. clearly shown next to the order placement time.