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>

apps/app/src/composables/api/useEvents.ts

@@ -132,6 +132,29 @@ export function useUpdateEvent(orgId: Ref<string>, id: Ref<string>) {
   })
 }
 
+export function useUploadEventImage(orgId: Ref<string>, eventId: Ref<string>) {
+  const queryClient = useQueryClient()
+
+  return useMutation({
+    mutationFn: async ({ file, type }: { file: File; type: 'banner' | 'logo' }) => {
+      const formData = new FormData()
+      formData.append('image', file)
+      formData.append('type', type)
+
+      const { data } = await apiClient.post<{ url: string }>(
+        `/organisations/${orgId.value}/events/${eventId.value}/upload-image`,
+        formData,
+        { headers: { 'Content-Type': 'multipart/form-data' } },
+      )
+
+      return data.url
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['events', orgId.value, eventId.value] })
+    },
+  })
+}
+
 export function useEventStats(eventId: Ref<string>) {
   return useQuery({
     queryKey: ['events', eventId, 'stats'],