feat: event registration branding with vertical wizard layout

- Add registration_banner_url, registration_welcome_text, registration_logo_url
  columns to events table with migration
- Add uploadImage endpoint (POST .../upload-image) with form request validation
  for banner and logo images (jpg/png/webp, max 5MB)
- Include branding fields in EventResource and PublicRegistrationDataController
- Build registration settings UI in organizer event settings page with
  banner/logo upload and welcome text editor
- Redesign portal registration page: hero banner with gradient overlay,
  welcome text card, vertical step navigation (desktop) / horizontal chips
  (mobile), two-column form fields with density="comfortable"
- Update success page with event banner and consistent branding
- Seed welcome text for Echt Feesten 2026
- Add 9 PHPUnit tests covering image upload, branding fields in API responses

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

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

@@ -7,6 +7,7 @@ namespace App\Http\Controllers\Api\V1;
 use App\Http\Controllers\Controller;
 use App\Http\Requests\Api\V1\StoreEventRequest;
 use App\Http\Requests\Api\V1\UpdateEventRequest;
+use App\Http\Requests\Api\V1\UploadEventImageRequest;
 use App\Http\Resources\Api\V1\EventResource;
 use App\Models\Event;
 use App\Models\Organisation;
@@ -15,6 +16,7 @@ use Illuminate\Http\JsonResponse;
 use Illuminate\Http\Request;
 use Illuminate\Http\Resources\Json\AnonymousResourceCollection;
 use Illuminate\Support\Facades\Gate;
+use Illuminate\Support\Facades\Storage;
 
 final class EventController extends Controller
 {
@@ -126,6 +128,24 @@ final class EventController extends Controller
         return EventResource::collection($children);
     }
 
+    public function uploadImage(UploadEventImageRequest $request, Organisation $organisation, Event $event): JsonResponse
+    {
+        Gate::authorize('update', [$event, $organisation]);
+
+        $path = $request->file('image')->store(
+            "events/{$event->id}",
+            'public'
+        );
+
+        $field = $request->type === 'banner'
+            ? 'registration_banner_url'
+            : 'registration_logo_url';
+
+        $event->update([$field => Storage::disk('public')->url($path)]);
+
+        return response()->json(['url' => $event->fresh()->{$field}]);
+    }
+
     public function stats(Event $event): JsonResponse
     {
         Gate::authorize('view', $event);