Enables all-day event conversion on column hover

Allows users to convert all-day events to timed events by dragging them over a day column.

This implementation adds logic to the DragDropManager to detect when an all-day event is dragged over a column.
It then emits a new event, 'drag:mouseenter-column', carrying the event data and target column information.

The event rendering service handles this event.

src/types/EventTypes.ts

@@ -67,6 +67,18 @@ export interface DragMouseLeaveHeaderEventPayload {
   draggedClone: HTMLElement| null;
 }
 
+// Drag mouse enter column event payload
+export interface DragMouseEnterColumnEventPayload {
+  targetColumn: ColumnBounds;
+  mousePosition: MousePosition;
+  snappedY: number;
+  originalElement: HTMLElement | null;
+  draggedClone: HTMLElement;
+  calendarEvent: CalendarEvent;
+  // Delegate pattern - allows subscriber to replace the dragged clone
+  replaceClone: (newClone: HTMLElement) => void;
+}
+
 // Drag column change event payload
 export interface DragColumnChangeEventPayload {
   originalElement: HTMLElement;