implement calendar event display with day indicators and overlay

- Add ExpandedEvent type to shared package for recurring event instances
- Implement EventController and EventService with full CRUD operations
- Server-side recurring event expansion via recurrenceExpander
- Calendar grid shows orange dot indicator for days with events
- Tap on day opens modal overlay with EventCards
- EventCard component with Feather icons (calendar, clock, repeat, edit, trash)
- EventsStore with Zustand for client-side event state management
- Load events for visible grid range including adjacent month days
- Add textPrimary, borderPrimary, eventIndicator to theme
- Update test responses for multiple events on Saturdays

packages/shared/src/models/CalendarEvent.ts

@@ -31,3 +31,8 @@ export interface UpdateEventDTO {
   isRecurring?: boolean;
   recurrenceRule?: string;
 }
+
+export interface ExpandedEvent extends CalendarEvent {
+  occurrenceStart: Date;
+  occurrenceEnd: Date;
+}