Fix mobile responsiveness across all pages

- BookingsPage: hide Номер/Выезд/Источник columns on small screens, show nights inline on mobile
- GuestsPage: stats grid 2→4 cols (grid-cols-2 lg:grid-cols-4), table columns hidden on mobile (md/lg breakpoints), GuestModal stats 2→4 cols on sm+
- BookingDetailPanel: full-width on mobile (w-full sm:w-[400px])
- Topbar: notifications panel full-width on mobile (w-[calc(100vw-1rem)] sm:w-96)
- LoyaltyPage, MaintenancePage, DiscountsPage, TariffsPage: stats grids grid-cols-2 lg:grid-cols-4

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

src/components/layout/Topbar.tsx

@@ -58,7 +58,7 @@ function NotificationsPanel({ onClose }: { onClose: () => void }) {
     : notifications
 
   return (
-    <div className="absolute right-0 top-full mt-2 w-96 max-w-[calc(100vw-1rem)] bg-white dark:bg-slate-800 border border-slate-200 dark:border-slate-700 rounded-2xl shadow-2xl z-20 flex flex-col" style={{ maxHeight: 'calc(100vh - 80px)' }}>
+    <div className="absolute right-0 top-full mt-2 w-[calc(100vw-1rem)] sm:w-96 bg-white dark:bg-slate-800 border border-slate-200 dark:border-slate-700 rounded-2xl shadow-2xl z-20 flex flex-col" style={{ maxHeight: 'calc(100vh - 80px)' }}>
       {/* Header */}
       <div className="flex items-center justify-between px-4 py-3 border-b border-slate-100 dark:border-slate-700 shrink-0">
         <div className="flex items-center gap-2">