Add Guests page with history/ratings and booking discounts

- New /guests page: searchable guest list with stay history, payment
  summary, rating (1-5 stars), loyalty status (Базовый/Серебряный/Золотой),
  tags (VIP, Постоянный, Корпоративный, Медовый месяц, Проблемный),
  per-guest notes, inline payments tab with debt tracking
- Guest detail modal: 3 tabs — Обзор / История проживания / Платежи
- Sidebar: added "Гости" link (UsersRound icon) in Основное section
- BookingModal: discount block — % or fixed ₽ amount, free-stay checkbox
  that zeroes room cost; summary shows strikethrough original + discount line;
  total reflects discount applied before services

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

src/components/layout/Sidebar.tsx

@@ -1,7 +1,7 @@
 import { NavLink, useNavigate } from 'react-router-dom'
 import {
   CalendarDays, BookOpen, BedDouble, Globe, Settings,
-  FileText, LayoutDashboard, Building2, Users, X, Hotel, Puzzle, CalendarRange, Map, LayoutGrid, UserCog,
+  FileText, LayoutDashboard, Building2, Users, X, Hotel, Puzzle, CalendarRange, Map, LayoutGrid, UserCog, UsersRound,
 } from 'lucide-react'
 import { useAuth } from '../../contexts/AuthContext'
 import { useModules } from '../../contexts/ModulesContext'
@@ -120,6 +120,7 @@ export function Sidebar({ open, onClose }: SidebarProps) {
               {!isHousekeeper && (
                 <>
                   <NavItem to="/bookings"        icon={BookOpen}     label="Бронирования"      onClick={onClose} />
+                  <NavItem to="/guests"          icon={UsersRound}   label="Гости"             onClick={onClose} />
                   <NavItem to="/rooms"            icon={BedDouble}    label="Номера"            onClick={onClose} />
                   <NavItem to="/room-categories" icon={LayoutGrid}   label="Категории номеров" onClick={onClose} />
                   <NavItem to="/availability"    icon={CalendarRange} label="Доступность"      onClick={onClose} />