feat(api): extend registration endpoints with dynamic fields and section preferences

- PublicRegistrationData now returns registration_fields (portal-visible only),
  form toggles, and available_tags for tag_picker fields
- Volunteer registration accepts field_values and section_preferences with
  festival_section_id, processed via existing services
- PortalMe eager-loads fieldValues and sectionPreferences
- Section preferences now use the proper relational table instead of custom_fields JSON

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

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

@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Http\Controllers\Api\V1;
+
+use App\Http\Controllers\Controller;
+use App\Http\Requests\Api\V1\PortalMeRequest;
+use App\Http\Resources\Api\V1\PersonResource;
+use App\Models\Event;
+use App\Models\Person;
+use Illuminate\Http\JsonResponse;
+
+final class PortalMeController extends Controller
+{
+    public function index(PortalMeRequest $request): JsonResponse
+    {
+        $event = Event::findOrFail($request->validated('event_id'));
+
+        if ($event->isSubEvent()) {
+            $event = $event->parent;
+        }
+
+        $person = Person::where('user_id', $request->user()->id)
+            ->where('event_id', $event->id)
+            ->with([
+                'crowdType',
+                'shiftAssignments.shift.festivalSection',
+                'shiftAssignments.shift.timeSlot',
+                'volunteerAvailabilities.timeSlot',
+                'fieldValues.registrationFormField',
+                'sectionPreferences.festivalSection',
+            ])
+            ->first();
+
+        if (! $person) {
+            return $this->notFound('No registration found for this event');
+        }
+
+        return $this->success(new PersonResource($person));
+    }
+}