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/Resources/Api/V1/EventResource.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace App\Http\Resources\Api\V1;
 
+use App\Models\Event;
 use Illuminate\Http\Request;
 use Illuminate\Http\Resources\Json\JsonResource;
 
@@ -21,6 +22,7 @@ final class EventResource extends JsonResource
             'end_date' => $this->end_date->toDateString(),
             'timezone' => $this->timezone,
             'status' => $this->status,
+            'allowed_transitions' => Event::STATUS_TRANSITIONS[$this->status] ?? [],
             'event_type' => $this->event_type,
             'event_type_label' => $this->event_type_label,
             'sub_event_label' => $this->sub_event_label,