Fixes drag and drop to header issues

Addresses two key issues related to dragging events to the header: the premature removal of the original event element and the creation of duplicate all-day events.

The original event is no longer removed when dragging to the header; it is now only removed upon a successful drop.

Also, it prevents the creation of duplicate all-day events by checking for existing all-day events before creating new ones, using DOM queries to ensure accurate state.

src/managers/ViewManager.ts

@@ -150,8 +150,8 @@ export class ViewManager {
         // Update button states using cached elements
         this.updateAllButtons();
         
-        // Trigger a calendar refresh to apply the new workweek
-        this.eventBus.emit(CoreEvents.REFRESH_REQUESTED);
+        // Trigger a workweek change to apply the new workweek
+        this.eventBus.emit(CoreEvents.WORKWEEK_CHANGED);
     }
 
     /**