feat: registration section preferences with show_in_registration filtering and deduplication

Add show_in_registration and registration_description columns to festival_sections.
Registration form now shows deduplicated sections by name (across sub-events),
filtered by show_in_registration=true, grouped by category with card-based UI.
Section preferences use section_name instead of section_id.
Add GET/PUT registration-settings endpoints for festival-level bulk management.

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

api/app/Http/Requests/Api/V1/UpdateRegistrationSettingsRequest.php

@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Http\Requests\Api\V1;
+
+use Illuminate\Foundation\Http\FormRequest;
+
+final class UpdateRegistrationSettingsRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return true;
+    }
+
+    /** @return array<string, mixed> */
+    public function rules(): array
+    {
+        return [
+            'name' => ['required', 'string', 'max:255'],
+            'show_in_registration' => ['required', 'boolean'],
+            'registration_description' => ['nullable', 'string', 'max:500'],
+        ];
+    }
+}