Refactors event positioning and drag-and-drop

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.

src/renderers/AllDayEventRenderer.ts

@@ -1,15 +1,61 @@
-// All-day event rendering using factory pattern
-
 import { CalendarEvent } from '../types/CalendarTypes';
 import { SwpAllDayEventElement } from '../elements/SwpEventElement';
-import { DateCalculator } from '../utils/DateCalculator';
 
 /**
- * AllDayEventRenderer - Handles rendering of all-day events in header row
- * Uses factory pattern with SwpAllDayEventElement for clean DOM creation
+ * AllDayEventRenderer - Simple rendering of all-day events
+ * Handles adding and removing all-day events from the header container
  */
 export class AllDayEventRenderer {
-  
+  private container: HTMLElement | null = null;
 
-  
+  constructor() {
+    this.getContainer();
+  }
+
+  /**
+   * Get or cache all-day container
+   */
+  private getContainer(): HTMLElement | null {
+    if (!this.container) {
+      const header = document.querySelector('swp-calendar-header');
+      if (header) {
+        this.container = header.querySelector('swp-allday-container');
+      }
+    }
+    return this.container;
+  }
+
+  /**
+   * Render an all-day event using factory pattern
+   */
+  public renderAllDayEvent(event: CalendarEvent, targetDate: string): HTMLElement | null {
+    const container = this.getContainer();
+    if (!container) return null;
+
+    const allDayElement = SwpAllDayEventElement.fromCalendarEvent(event, targetDate);
+    const element = allDayElement.getElement();
+    
+    container.appendChild(element);
+    return element;
+  }
+
+  /**
+   * Remove an all-day event by ID
+   */
+  public removeAllDayEvent(eventId: string): void {
+    const container = this.getContainer();
+    if (!container) return;
+
+    const eventElement = container.querySelector(`swp-allday-event[data-event-id="${eventId}"]`);
+    if (eventElement) {
+      eventElement.remove();
+    }
+  }
+
+  /**
+   * Clear cache when DOM changes
+   */
+  public clearCache(): void {
+    this.container = null;
+  }
 }