feat: festival/series model with sub-events, cross-event sections, tab navigation, SectionsShiftsPanel extraction

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -17,12 +17,12 @@ final class UpdateEventRequest extends FormRequest
     public function rules(): array
     {
         return [
+            // Status changes must go through POST /events/{event}/transition
             'name' => ['sometimes', 'string', 'max:255'],
             'slug' => ['sometimes', 'string', 'max:255', 'regex:/^[a-z0-9-]+$/'],
             'start_date' => ['sometimes', 'date'],
             'end_date' => ['sometimes', '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' => ['sometimes', 'in:event,festival,series'],
             'event_type_label' => ['nullable', 'string', 'max:50'],