Refactors date handling for ISO week compatibility

Centralizes all date calculations into a new `DateCalculator` class for better maintainability and consistency.

Ensures correct ISO week handling (Monday as the first day) throughout the calendar.

Updates `CalendarConfig` to use ISO day numbering (1-7 for Mon-Sun) for work week definitions.

Fixes issue where date calculations were inconsistent.
Enhances event rendering and navigation.
Updates navigation logic to use pre-rendered events.
Removes the need for `CONTAINER_READY_FOR_EVENTS` event.

src/managers/ViewManager.ts

@@ -36,6 +36,7 @@ export class ViewManager {
         
         // Setup workweek preset button handlers
         this.setupWorkweekButtonHandlers();
+        
     }
 
     private setupViewButtonHandlers(): void {
@@ -64,6 +65,7 @@ export class ViewManager {
         });
     }
 
+
     private initializeView(): void {
         this.updateViewButtons();
         this.updateWorkweekButtons();