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

apps/server/src/utils/recurrenceExpander.ts

@@ -1,10 +1,5 @@
 import { RRule, rrulestr } from "rrule";
-import { CalendarEvent } from "@caldav/shared";
-
-export interface ExpandedEvent extends CalendarEvent {
-  occurrenceStart: Date;
-  occurrenceEnd: Date;
-}
+import { CalendarEvent, ExpandedEvent } from "@caldav/shared";
 
 // Convert local time to "fake UTC" for rrule
 // rrule interprets all dates as UTC internally, so we need to trick it