Add drag & drop for entries and per-stay band colours

Calendar chips can be dragged onto another in-range day (multi-day entries shift end_date by the same delta in one PATCH); day-editor rows get a drag handle to reorder within a day, patching sort_order only for changed positions. Continues/dropoff ghost chips and stay bands are not draggable; touch devices fall back to the existing click/edit flow. Each stay band now gets a deterministic colour from an 8-hue palette by chronological index, mirrored as dots in the summary Areas list.

public/js/views/calendar.js

@@ -16,6 +16,7 @@ import {
   isMultiDay,
 } from '../format.js';
 import { computeStayLayout, renderWeekBands } from './stayBands.js';
+import { makeChipDraggable, makeDayDropTarget } from './dragdrop.js';
 
 const WEEKDAYS = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'];
 
@@ -54,6 +55,8 @@ export function renderCalendar(tctx) {
   }
 
   const stayLayout = computeStayLayout(entries);
+  // id -> entry, for the drop handler to resolve the dragged chip.
+  const entriesById = new Map(entries.map((e) => [e.id, e]));
 
   const rangeStart = parseYMD(trip.start_date);
   const rangeEnd = parseYMD(trip.end_date);
@@ -97,17 +100,23 @@ export function renderCalendar(tctx) {
     if (bands) weekEl.appendChild(bands);
     const daysRow = el('div', { class: 'cal-week-days' });
     for (const date of week) {
-      daysRow.appendChild(dayCell(date, rangeStart, rangeEnd, byDate, contByDate, dropoffByDate, tctx, currency));
+      daysRow.appendChild(dayCell(date, rangeStart, rangeEnd, byDate, contByDate, dropoffByDate, entriesById, tctx, currency));
     }
     weekEl.appendChild(daysRow);
     cal.appendChild(weekEl);
   }
 
+  // A cancelled drag (released outside a cell) fires dragend on the source chip,
+  // which bubbles up here — sweep any lingering drop highlight.
+  cal.addEventListener('dragend', () => {
+    for (const n of cal.querySelectorAll('.cal-day-drop')) n.classList.remove('cal-day-drop');
+  });
+
   section.appendChild(cal);
   return section;
 }
 
-function dayCell(date, rangeStart, rangeEnd, byDate, contByDate, dropoffByDate, tctx, currency) {
+function dayCell(date, rangeStart, rangeEnd, byDate, contByDate, dropoffByDate, entriesById, tctx, currency) {
   const key = ymd(date);
   const inRange = date >= rangeStart && date <= rangeEnd;
   // Stays render as bands, not chips, so exclude them from the day cell.
@@ -158,6 +167,12 @@ function dayCell(date, rangeStart, rangeEnd, byDate, contByDate, dropoffByDate,
     });
   }
 
+  // Only in-range days accept dropped entries; new sort_order appends after the
+  // day's current entries (byDate holds every entry, incl. stays, for that day).
+  if (inRange) {
+    makeDayDropTarget(cell, key, (byDate.get(key) || []).length, entriesById, tctx);
+  }
+
   return cell;
 }
 
@@ -167,7 +182,7 @@ function chip(entry, currency) {
   const chain = hasSegments(entry) ? flightChain(entry.segments) : '';
   const car = hasRental(entry) ? [entry.rental.brand, entry.rental.model].filter(Boolean).join(' ') : '';
   const label = chain || car || entry.title;
-  return el(
+  const node = el(
     'div',
     {
       class: 'cal-chip',
@@ -180,6 +195,10 @@ 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.
+  makeChipDraggable(node, entry);
+  return node;
 }
 
 // Ghost chip on the days a multi-day entry spans after its start. Clicking