Calendar: hide cancelled bookings, drag-to-move rooms, allow booking through checked-out

- Filter cancelled bookings from calendar grid (they no longer appear as red blocks)
- Remove cancelled from legend
- Drag-to-move: left-click drag a booking block to a different room row; click without dragging still opens the detail panel
- checked_out bookings are now semi-transparent and pointer-events-none so clicking through them creates a new booking
- Conflict detection in BookingDetailPanel now excludes checked_out bookings

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

src/components/bookings/BookingDetailPanel.tsx

@@ -81,6 +81,7 @@ export function BookingDetailPanel({ booking, room, rooms, allBookings, onClose,
       b.roomId === rid &&
       b.status !== 'cancelled' &&
       b.status !== 'no_show' &&
+      b.status !== 'checked_out' &&
       b.checkIn < co && b.checkOut > ci,
     ) ?? null