Centralizes event position calculations into `PositionUtils` for consistency and reusability across managers and renderers.
Improves drag-and-drop functionality by emitting events for all-day event conversion and streamlining position calculations during drag operations.
Introduces `AllDayManager` and `AllDayEventRenderer` to manage and render all-day events in the calendar header. This allows dragging events to the header to convert them to all-day events.
