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.

wwwroot/css/calendar-components-css.css

@@ -125,6 +125,7 @@ swp-preset-button {
   }
 }
 
+
 /* Search container */
 swp-search-container {
   margin-left: auto;