Make stay bands draggable to move stays between days

Dragging any week-segment of a stay band onto an in-range day moves the
whole stay there, preserving its length (same one-PATCH date+end_date
shift the multi-day chips use). Clicking a band still opens the editor.

public/js/views/calendar.js

@@ -196,8 +196,9 @@ function chip(entry, currency) {
       ? el('span', { class: 'chip-price' }, formatMoney(entry.price, currency, { compact: true }))
       : null,
   );
-  // Regular chips are drag sources (move the entry to another day). The
-  // "…continues" and "dropoff" ghost chips and stay bands stay non-draggable.
+  // Regular chips are drag sources (move the entry to another day), same as
+  // stay area bands (see stayBands.js). The "…continues" and "dropoff" ghost
+  // chips stay non-draggable — they're derived markers, not the entry itself.
   makeChipDraggable(node, entry);
   return node;
 }