3.5 Move, resize and reschedule

Drag a booking on the grid to change the time; drag to another column to change the
professional / service / space.
Resize from the edge (bottom on the grid, right on the Gantt) to change the duration.
Each change asks for confirmation and is validated (hours, conflicts, staff schedule,
capacity/exclusivity of spaces). If invalid, it's rejected with a message.
On rescheduling, the customer is notified ("Changed") and the reminder is re-armed.
On mobile: press and hold ~0.3 s on the booking until it "lifts" (vibrates) before
dragging/resizing — so you don't move it by accident while scrolling. A quick tap opens Details.
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03-drag.png — A booking being dragged to another column/time, with the confirm modal.