feat: add a booking event history for admins

Admins get /admin/history: one line per booking created, rescheduled or
released, per series created or ended, and per resource deleted with its
bookings. Sortable by time, kind, resource, booked day and both people;
filterable by period, kinds, who acted and resource type.

Events are snapshots written inside the same transaction as the change,
so a rolled-back booking leaves none and a released booking stays
readable. app:booking-events:prune keeps twelve months and needs a cron
entry on the server.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

assets/icons/lucide/history.svg

@@ -0,0 +1 @@
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