Fix booking creation: localStorage token, conflict detection, paid_amount

- Fix api.ts getToken/saveToken to read from localStorage (matching AuthContext) — was reading sessionStorage causing all API requests to fail auth until refresh
- Fix session cleanup on 401 to use localStorage
- Add isConflict/availableRooms helpers to BookingModal; show amber warning when selected room is occupied with clickable free room suggestions
- Pass bookings prop to BookingModal via BookingCalendar
- Add paid_amount to backend POST /bookings INSERT
- Show alert() when booking creation fails so user sees the error
- Pass paidAmount in CalendarPage handleCreate

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

src/pages/CalendarPage.tsx

@@ -58,13 +58,15 @@ export function CalendarPage() {
         checkIn: data.checkIn, checkOut: data.checkOut,
         adults: data.adults, children: data.children,
         status: data.status, source: data.source,
-        totalAmount: data.totalAmount, notes: data.notes,
+        totalAmount: data.totalAmount, paidAmount: data.paidAmount, notes: data.notes,
       })
       setBookings(prev => [...prev, created])
       send({ type: 'booking:created', booking: created })
       if (data.roomId) send({ type: 'unlock', roomId: data.roomId })
     } catch (err) {
       console.error('Failed to create booking:', err)
+      const msg = err instanceof Error ? err.message : 'Ошибка создания бронирования'
+      alert(msg)
     }
   }