feat: add recurring event deletion with three modes

Implement three deletion modes for recurring events:
- single: exclude specific occurrence via EXDATE mechanism
- future: set RRULE UNTIL to stop future occurrences
- all: delete entire event series

Changes include:
- Add exceptionDates field to CalendarEvent model
- Add RecurringDeleteMode type and DeleteRecurringEventDTO
- EventService.deleteRecurring() with mode-based logic using rrule library
- EventController DELETE endpoint accepts mode/occurrenceDate query params
- recurrenceExpander filters out exception dates during expansion
- AI tools support deleteMode and occurrenceDate for proposed deletions
- ChatService.confirmEvent() handles recurring delete modes
- New DeleteEventModal component for unified delete confirmation UI
- Calendar screen integrates modal for both recurring and non-recurring events

apps/client/src/components/EventConfirmDialog.tsx

@@ -29,7 +29,9 @@ const EventConfirmDialog = ({
     <Modal visible={false} transparent animationType="fade">
       <View>
         <Pressable>
-          <Text style={{ color: theme.textPrimary }}>EventConfirmDialog - Not Implemented</Text>
+          <Text style={{ color: theme.textPrimary }}>
+            EventConfirmDialog - Not Implemented
+          </Text>
         </Pressable>
       </View>
     </Modal>