Adds header drawer event rendering support

Extends calendar rendering to support all-day events in header drawer

Implements rendering logic for all-day events in header drawer:
- Fetches events for visible date range
- Filters and creates header items for all-day events
- Dynamically positions events with color classes
- Expands header drawer when events are present

Enhances event persistence with header drop detection

src/v2/managers/EventPersistenceManager.ts

@@ -41,11 +41,13 @@ export class EventPersistenceManager {
     }
 
     // Update and save - start/end already calculated in SwpEvent
+    // If dropped in header, mark as allDay
     const updatedEvent: ICalendarEvent = {
       ...event,
       start: swpEvent.start,
       end: swpEvent.end,
       resourceId: swpEvent.resourceId ?? event.resourceId,
+      allDay: payload.target === 'header' ? true : event.allDay,
       syncStatus: 'pending'
     };