fix: correct recurring to non-recurring event update logic

- Fix bug where updating recurring event to non-recurring created duplicate events
- Deduplicate URLs before deletion to avoid multiple delete calls on same file
- Add onCloseAll prop to close both preview and update modals after save
- Adjust smooth UI

Resolves issue where repeat->no-repeat conversion left old recurring events visible

src/features/Events/EventDisplayPreview.tsx

@@ -510,6 +510,10 @@ export default function EventPreviewModal({
       <EventUpdateModal
         open={openUpdateModal}
         onClose={() => setOpenUpdateModal(false)}
+        onCloseAll={() => {
+          setOpenUpdateModal(false);
+          onClose({}, "backdropClick");
+        }}
         eventId={eventId}
         calId={calId}
         typeOfAction={typeOfAction}