Fix mobile UI bugs from screenshots

- Notifications panel: fixed positioning on mobile (full-width below topbar,
  no more overflow behind calendar)
- BookingModal: two-column layout stacks vertically on mobile (flex-col sm:flex-row)
- TariffsPage cards: price + actions merged into right column, no text overlap
- DiscountsPage cards: same fix, price text reduced to text-lg
- ReviewsPage: action buttons moved inside content div (no longer overlap guest name)
- RoomCategoriesPage: edit/delete buttons stack as column, 'Номера' text hidden on mobile
- PosPage: show desktop-only message on mobile instead of broken layout

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

src/components/bookings/BookingModal.tsx

@@ -223,7 +223,7 @@ export function BookingModal({ open, draft, rooms, onClose, onSave, existing }:
         {/* ── BOOKING TAB ── */}
         {activeTab === 'booking' && (
         <div className="space-y-4">
-        <div className="flex gap-6">
+        <div className="flex flex-col sm:flex-row gap-4 sm:gap-6">
           {/* ── LEFT COLUMN ── */}
           <div className="flex-1 space-y-3 min-w-0">
             {/* Room */}