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/database/migrations/2026_04_17_200000_add_display_width_to_registration_fields_tables.php

@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('registration_form_fields', function (Blueprint $table) {
+            $table->string('display_width', 10)->default('full')->after('sort_order');
+        });
+
+        Schema::table('registration_field_templates', function (Blueprint $table) {
+            $table->string('display_width', 10)->default('full')->after('sort_order');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('registration_form_fields', function (Blueprint $table) {
+            $table->dropColumn('display_width');
+        });
+
+        Schema::table('registration_field_templates', function (Blueprint $table) {
+            $table->dropColumn('display_width');
+        });
+    }
+};