Bulk-deleting all events on the current page left the list empty until
manual reload. After the React Query refetch returned `events: []` with
a smaller `totalPages`, the page state was stuck on the old (now
out-of-range) page index — the backend correctly serves an empty page
for `page > totalPages`, but the UI had no logic to step back.
Add a useEffect that watches `data.pagination.totalPages` against the
current `page` and resets `page = max(1, totalPages)` whenever the
result count shrinks. Fires after every refetch so it covers bulk
delete, individual delete, archive, and any filter change that
shrinks the result set — same one-line guarantee.
Reported by @Rekoo-PS in #442.
Paul Nothaft
9c4a96fe97