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/routes/api.php

@@ -129,6 +129,8 @@ Route::middleware('auth:sanctum')->group(function () {
     Route::prefix('events/{event}')->group(function () {
         Route::apiResource('locations', LocationController::class)
             ->except(['show']);
+        Route::get('sections/registration-settings', [FestivalSectionController::class, 'registrationSettings']);
+        Route::put('sections/registration-settings', [FestivalSectionController::class, 'updateRegistrationSettings']);
         Route::apiResource('sections', FestivalSectionController::class)
             ->except(['show']);
         Route::post('sections/reorder', [FestivalSectionController::class, 'reorder']);