feat: festival/event model frontend + topbar activeren

- Events lijst: card grid met festival/serie chips
- Festival detail: programmaonderdelen grid
- CreateSubEventDialog voor sub-events binnen festival
- EventTabsNav: breadcrumb terug naar festival
- Sessie A: festival-bewuste EventResource + children endpoint
- Topbar: zoekbalk, theme switcher, shortcuts, notificaties
- Schema v1.7 + BACKLOG.md toegevoegd
- 121 tests groen

api/app/Http/Requests/Api/V1/StoreEventRequest.php

@@ -23,6 +23,10 @@ final class StoreEventRequest extends FormRequest
             'end_date' => ['required', 'date', 'after_or_equal:start_date'],
             'timezone' => ['sometimes', 'string', 'max:50'],
             'status' => ['sometimes', 'string', 'in:draft,published,registration_open,buildup,showday,teardown,closed'],
+            'parent_event_id' => ['nullable', 'ulid', 'exists:events,id'],
+            'event_type' => ['nullable', 'in:event,festival,series'],
+            'event_type_label' => ['nullable', 'string', 'max:50'],
+            'sub_event_label' => ['nullable', 'string', 'max:50'],
         ];
     }
 }