Connect ChannelsPage, FloorMapPage, SettingsPage, UsersPage to real API

- ChannelsPage: load from API, toggle/sync call real endpoints; normalize
  enabled→isEnabled, lastSyncedAt→lastSyncAt, add displayName/mappings defaults
- FloorMapPage: load rooms+bookings from API; create booking via API
- SettingsPage: load hotel via GET /api/hotels/:slug; save general section
  via PATCH (name, address, timezone, currency, check_in/out times)
- UsersPage: load users from API; create/update/delete via API;
  map backend User (name/role) → StaffUser (firstName/lastName/StaffRole)
- api.ts: add hotels.get/update, users.delete, channel normalization,
  HotelPayload/toHotelPayload
- types/index.ts: extend Hotel with phone/checkInTime/checkOutTime/optional fields;
  add User.createdAt/updatedAt
- backend/routes/hotels.ts: extend PATCH to allow address/phone/check_in_time/check_out_time
- backend/migrations/004_hotels_contacts.sql: add address/phone/check_in/out_time to hotels

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

backend/migrations/004_hotels_contacts.sql

@@ -0,0 +1,6 @@
+-- Migration 004 — Add contact/schedule fields to hotels
+ALTER TABLE hotels
+  ADD COLUMN IF NOT EXISTS address        TEXT,
+  ADD COLUMN IF NOT EXISTS phone          VARCHAR(50),
+  ADD COLUMN IF NOT EXISTS check_in_time  TIME NOT NULL DEFAULT '14:00',
+  ADD COLUMN IF NOT EXISTS check_out_time TIME NOT NULL DEFAULT '12:00';