Add maintenance severity levels, notifications context, and widget payment step

- HousekeepingPage: 3-level severity for maintenance reports (Не срочно / Средняя / Экстренно!); Экстренно automatically blocks the room and triggers an urgent notification; severity displayed as colored badge on task card
- NotificationsContext: extract shared notifications state from Topbar into context so any page can push notifications; add 'maintenance' type with wrench icon
- Topbar: migrate to NotificationsContext; add maintenance notification type with red Wrench icon
- BookingWidgetPage: add payment step after guest form when payment provider is connected (card number/expiry/CVV/name form); Без оплаты mode skips payment and shows "pay on site" message; hourly services (unit='ч') show date + time-from/time-to picker in form step

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

src/types/index.ts

@@ -175,6 +175,8 @@ export interface HousekeepingTask {
   status: 'pending' | 'in_progress' | 'done'
   notes?: string
   maintenanceNote?: string
+  maintenanceSeverity?: 'low' | 'medium' | 'high'
+  roomBlocked?: boolean
   dueDate: string
   completedAt?: string
   type: 'cleaning' | 'inspection' | 'maintenance'