feat: widget additional services — sourced from rental objects module

- Additional services in widget are now derived from rental_objects (not a separate list)
- Settings page shows rental objects with enable/disable toggle; link to rental module
- Saves only {id, enabled}[] to widget_services — rental objects manage name/price/icon
- Standalone widget also derives additionalServices from config.rentalObjects
- Widget config API includes services[] in widgetSettings

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/routes/publicWidget.ts

@@ -78,6 +78,7 @@ const publicWidget: FastifyPluginAsync = async (fastify) => {
         allowChildren:   (ws.widget_children    as boolean) ?? true,
         hotelName:       (ws.widget_hotel_name  as string)  ?? hotel.name,
         bankDetails:     (ws.widget_bank_details as string) ?? '',
+        services:        Array.isArray(ws.widget_services) ? ws.widget_services as { id: string; enabled: boolean }[] : null,
       },
       rooms: rooms.map(r => ({
         id: r.id,