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/stores/ThemeStore.ts

@@ -8,5 +8,5 @@ interface ThemeState {
 
 export const useThemeStore = create<ThemeState>((set) => ({
   theme: THEMES.defaultLight,
-  setTheme: (themeName) => set({theme: THEMES[themeName]})
-}))
+  setTheme: (themeName) => set({ theme: THEMES[themeName] }),
+}));