Major UX improvements across multiple pages

Шахматка:
- Date/period picker dropdown on navigation button (choose start date + days window)
- Cancelled bookings fade out with animation after 1 second

Бронирования:
- Clickable column headers with sort asc/desc (Гость, Заезд, Выезд, Статус, Источник, Сумма)

Страница входа:
- Removed role-based account selector — just email + password
- System auto-detects role/hotel from credentials

Настройки:
- New "Бронирование" section with room assignment strategy (spread/together/sequential/manual)
- Notifications: SMTP email config + SMS provider config (SMSC, SMS.ru, МТС, etc.)

Модули:
- Added Housekeeping and Channel Manager as proper modules
- Channel Manager lists: Booking.com, Airbnb, Яндекс Путешествия, Островок, Суточно.ру, OneTwoTrip
- Housekeeping visible to all roles (including housekeeper) via module status
- Sidebar now uses module status to show/hide Уборка and Каналы

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

backend/src/config.ts

@@ -0,0 +1,22 @@
+export const config = {
+  port: parseInt(process.env.PORT ?? '3000', 10),
+  nodeEnv: process.env.NODE_ENV ?? 'development',
+
+  database: {
+    url: process.env.DATABASE_URL ?? 'postgresql://hotelsync:hotelsync@localhost:5432/hotelsync',
+  },
+
+  redis: {
+    url: process.env.REDIS_URL ?? 'redis://localhost:6379',
+  },
+
+  jwt: {
+    secret: process.env.JWT_SECRET ?? 'dev-secret-change-in-production',
+    accessExpiry: '1h',
+    refreshExpiry: 30 * 24 * 60 * 60, // 30 days in seconds
+  },
+
+  cors: {
+    origins: (process.env.CORS_ORIGINS ?? 'http://localhost:5173').split(',').map(s => s.trim()),
+  },
+}