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]>

templates/board/_floorplan.html.twig

@@ -40,12 +40,10 @@
                 <section>
                     {% if spot_group.group %}
                         {% set free = spot_group.freeCount %}
-                        {# Prominent on purpose: desk labels repeat from room to room, so the room is
-                           the only thing telling one "Schreibtisch 1" from the next. #}
-                        <h3 class="!mb-0 pb-2 text-base font-semibold text-gray-900 md:text-lg">
+                        <h3 class="!mb-0 pb-2 text-sm font-semibold text-gray-500 md:text-sm">
                             {{- spot_group.group.label -}}
-                            {%- if free > 0 %} <span class="text-sm font-normal text-emerald-600">· {{ free }} frei</span>
-                            {%- else %} <span class="text-sm font-normal text-gray-500">· belegt</span>{% endif -%}
+                            {%- if free > 0 %} <span class="text-emerald-600">· {{ free }} frei</span>
+                            {%- else %} <span>· belegt</span>{% endif -%}
                         </h3>
                     {% endif %}