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/Requests/Api/V1/VolunteerRegistrationRequest.php

@@ -35,6 +35,7 @@ final class VolunteerRegistrationRequest extends FormRequest
             'last_name' => ['required_without:_authenticated', 'string', 'max:255'],
             'email' => ['required_without:_authenticated', 'email', 'max:255'],
             'phone' => ['nullable', 'string', 'max:50'],
+            'date_of_birth' => ['nullable', 'date', 'before:today'],
 
             'tshirt_size' => ['nullable', 'string', 'in:XS,S,M,L,XL,XXL,XXXL'],
             'first_aid' => ['nullable', 'boolean'],