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/Models/Person.php

@@ -30,6 +30,7 @@ final class Person extends Model
         'company_id',
         'first_name',
         'last_name',
+        'date_of_birth',
         'email',
         'phone',
         'status',
@@ -51,6 +52,7 @@ final class Person extends Model
     protected function casts(): array
     {
         return [
+            'date_of_birth' => 'date',
             'is_blacklisted' => 'boolean',
             'custom_fields' => 'array',
         ];