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/app/register.tsx

@@ -51,7 +51,10 @@ const RegisterScreen = () => {
         </Text>
 
         {error && (
-          <Text className="mb-4 text-center" style={{ color: theme.rejectButton }}>
+          <Text
+            className="mb-4 text-center"
+            style={{ color: theme.rejectButton }}
+          >
             {error}
           </Text>
         )}