Improves all-day event drag and drop

Refactors all-day event conversion during drag and drop to
use the event payload, improving code clarity and reducing
redundancy.

Removes unnecessary style settings and fixes column detection
logic. Addresses an issue where event removal occurred before
successful placement.

src/elements/SwpEventElement.ts

@@ -88,7 +88,6 @@ export class SwpEventElement extends BaseEventElement {
    */
   private applyPositioning(): void {
     const position = this.calculateEventPosition();
-    this.element.style.position = 'absolute';
     this.element.style.top = `${position.top + 1}px`;
     this.element.style.height = `${position.height - 3}px`;
     this.element.style.left = '2px';