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/App.tsx

@@ -26,6 +26,7 @@ import { RentalPage } from './pages/RentalPage'
 import { RoomCategoriesPage } from './pages/RoomCategoriesPage'
 import { DocumentsPage } from './pages/DocumentsPage'
 import { UsersPage } from './pages/UsersPage'
+import { GuestsPage } from './pages/GuestsPage'
 
 export default function App() {
   return (
@@ -61,6 +62,7 @@ export default function App() {
                 <Route path="/room-categories" element={<RoomCategoriesPage />} />
                 <Route path="/documents"       element={<DocumentsPage />} />
                 <Route path="/users"           element={<UsersPage />} />
+                <Route path="/guests"          element={<GuestsPage />} />
               </Route>
 
               {/* Admin routes */}