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/pages/PosPage.tsx

@@ -202,6 +202,22 @@ export function PosPage() {
   return (
     <div className="flex h-full flex-col">
 
+      {/* ── Desktop-only notice on mobile ── */}
+      <div className="sm:hidden flex-1 flex flex-col items-center justify-center gap-4 p-8 text-center">
+        <div className="w-16 h-16 rounded-2xl bg-slate-100 dark:bg-slate-700 flex items-center justify-center">
+          <Receipt size={28} className="text-slate-400" />
+        </div>
+        <div>
+          <p className="text-lg font-semibold text-slate-700 dark:text-slate-300">Касса — только десктоп</p>
+          <p className="text-sm text-slate-500 dark:text-slate-400 mt-1">
+            Откройте приложение на компьютере или планшете для работы с кассой
+          </p>
+        </div>
+      </div>
+
+      {/* ── Full POS UI (desktop only) ── */}
+      <div className="hidden sm:flex sm:flex-col sm:flex-1 sm:overflow-hidden">
+
       {/* ── Top bar ── */}
       <div className="shrink-0 px-4 py-3 border-b border-slate-200 dark:border-slate-700 bg-white dark:bg-slate-800">
         <div className="flex items-center justify-between flex-wrap gap-2">
@@ -875,6 +891,7 @@ export function PosPage() {
           </div>
         </div>
       )}
+      </div>{/* end desktop-only wrapper */}
     </div>
   )
 }