feat: full Room Service backend integration

- Migrations 086-088: room_service_settings, menu_items, orders+order_items
- Backend: /api/hotels/:slug/room-service/* routes (settings, menu CRUD,
  orders CRUD, public config, public order status)
- push.ts: sendPushToHotel() — push to all hotel staff on new order
- On new order: in-app notification + push to hotel staff
- api.ts: RoomService types + roomService API methods
- RoomServicePage: replaced mocked state with real API, 30s polling,
  add/edit/delete menu items modal, real advance/cancel order
- GuestRoomServicePage: fetches real menu + config, uses hotel payment
  methods, submits real order, polls status every 15s

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

backend/migrations/086_room_service_settings.sql

@@ -0,0 +1,12 @@
+-- Migration 086 — Room Service: settings per hotel
+
+CREATE TABLE room_service_settings (
+  hotel_id          UUID    PRIMARY KEY REFERENCES hotels(id) ON DELETE CASCADE,
+  is_active         BOOLEAN NOT NULL DEFAULT true,
+  service_charge_pct INTEGER NOT NULL DEFAULT 0,
+  updated_at        TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+-- Auto-create settings for existing hotels
+INSERT INTO room_service_settings (hotel_id)
+SELECT id FROM hotels ON CONFLICT DO NOTHING;