feat: registration form field display_width and option descriptions

Add configurable column widths (full/half) and optional descriptions
for radio/select/checkbox options on registration form fields.

- Migration adds display_width column to both tables
- FieldDisplayWidth enum with smart defaults per field type
- normalized_options accessor for backwards-compatible option format
- Portal form renderer uses display_width for VRow/VCol grid layout
- Radio/select/checkbox options render with descriptions
- Admin field editor supports display_width toggle and description input
- System templates updated with appropriate widths and descriptions

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

api/app/Http/Controllers/Api/V1/PublicRegistrationDataController.php

@@ -97,10 +97,12 @@ final class PublicRegistrationDataController extends Controller
                         'slug' => $field->slug,
                         'field_type' => $field->field_type->value,
                         'options' => $field->options,
+                        'normalized_options' => $field->normalized_options,
                         'tag_category' => $field->tag_category,
                         'is_required' => $field->is_required,
                         'section' => $field->section,
                         'help_text' => $field->help_text,
+                        'display_width' => $field->display_width->value,
                     ];
 
                     if ($field->field_type === \App\Enums\RegistrationFieldType::TAG_PICKER) {