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/Services/RegistrationFormFieldService.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace App\Services;
 
+use App\Enums\FieldDisplayWidth;
 use App\Enums\RegistrationFieldType;
 use App\Models\Event;
 use App\Models\Person;
@@ -30,6 +31,11 @@ final class RegistrationFormFieldService
     {
         $data['slug'] = $this->generateUniqueSlug($event, $data['label']);
 
+        if (!isset($data['display_width'])) {
+            $fieldType = RegistrationFieldType::from($data['field_type']);
+            $data['display_width'] = FieldDisplayWidth::defaultForFieldType($fieldType)->value;
+        }
+
         $field = RegistrationFormField::create([
             'event_id' => $event->id,
             ...$data,
@@ -173,6 +179,7 @@ final class RegistrationFormFieldService
                 'section' => $sourceField->section,
                 'help_text' => $sourceField->help_text,
                 'sort_order' => ++$maxOrder,
+                'display_width' => $sourceField->display_width,
             ]);
 
             $created->push($field);