feat: add date_of_birth field to persons across all layers

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

api/app/Http/Resources/Api/V1/PersonResource.php

@@ -16,6 +16,7 @@ final class PersonResource extends JsonResource
             'event_id' => $this->event_id,
             'first_name' => $this->first_name,
             'last_name' => $this->last_name,
+            'date_of_birth' => $this->date_of_birth?->toDateString(),
             'full_name' => $this->full_name,
             'email' => $this->email,
             'phone' => $this->phone,