Refactors calendar type to calendar mode

Updates the codebase to utilize `CalendarMode` instead of the deprecated `CalendarType`.

Simplifies `CalendarConfig` by removing legacy methods and related type aliases, enhancing code maintainability and clarity.

Improves event rendering by ensuring `GRID_RENDERED` events include explicit start and end dates, preventing errors and ensuring correct data filtering.

src/managers/CalendarManager.ts

@@ -144,7 +144,6 @@ export class CalendarManager {
         this.eventBus.emit(CoreEvents.DATE_CHANGED, {
             previousDate,
             currentDate: this.currentDate,
-            date: this.currentDate,  // Add for backward compatibility
             view: this.currentView
         });