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/managers/DragDropManager.ts

@@ -14,6 +14,7 @@ import {
   DragEndEventPayload,
   DragMouseEnterHeaderEventPayload,
   DragMouseLeaveHeaderEventPayload,
+  DragMouseEnterColumnEventPayload,
   DragColumnChangeEventPayload
 } from '../types/EventTypes';
 import { MousePosition } from '../types/DragDropTypes';
@@ -116,6 +117,8 @@ export class DragDropManager {
         const target = e.target as HTMLElement;
         if (target.closest('swp-calendar-header')) {
           this.handleHeaderMouseEnter(e as MouseEvent);
+        } else if (target.closest('swp-day-column')) {
+          this.handleColumnMouseEnter(e as MouseEvent);
         } else if (target.closest('swp-event')) {
           // Entered an event - activate hover tracking and set color
           const eventElement = target.closest<HTMLElement>('swp-event');
@@ -652,6 +655,46 @@ export class DragDropManager {
     }
   }
 
+  /**
+   * Handle mouse enter on day column - for converting all-day to timed events
+   */
+  private handleColumnMouseEnter(event: MouseEvent): void {
+    // Only handle if we're dragging an all-day event
+    if (!this.isDragStarted || !this.draggedClone || !this.draggedClone.hasAttribute('data-allday')) {
+      return;
+    }
+
+    console.log('🎯 DragDropManager: Mouse entered day column');
+
+    const position: MousePosition = { x: event.clientX, y: event.clientY };
+    const targetColumn = ColumnDetectionUtils.getColumnBounds(position);
+
+    if (!targetColumn) {
+      console.warn("No column detected when entering day column");
+      return;
+    }
+
+    // Calculate snapped Y position
+    const snappedY = this.calculateSnapPosition(position.y, targetColumn);
+
+    // Extract CalendarEvent from the dragged clone
+    const calendarEvent = SwpEventElement.extractCalendarEventFromElement(this.draggedClone);
+
+    const dragMouseEnterPayload: DragMouseEnterColumnEventPayload = {
+      targetColumn: targetColumn,
+      mousePosition: position,
+      snappedY: snappedY,
+      originalElement: this.draggedElement,
+      draggedClone: this.draggedClone,
+      calendarEvent: calendarEvent,
+      // Delegate pattern - allows EventRenderer to replace the clone
+      replaceClone: (newClone: HTMLElement) => {
+        this.draggedClone = newClone;
+      }
+    };
+    this.eventBus.emit('drag:mouseenter-column', dragMouseEnterPayload);
+  }
+
   /**
    * Handle mouse leave from calendar header - simplified using native events
    */