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/dayEditor.js

@@ -22,6 +22,7 @@ import {
 import { createFlightRoute, renderSegmentLines } from './segments.js';
 import { createRentalDetails, renderRentalLine } from './rental.js';
 import { createCostForm } from './costForm.js';
+import { enableRowReorder } from './dragdrop.js';
 
 export function openDayEditor(tctx, date) {
   // A form-state object for the entry currently being added/edited.
@@ -87,21 +88,35 @@ export function openDayEditor(tctx, date) {
     if (!dayEntries.length) {
       list.appendChild(el('p', { class: 'muted entry-empty' }, 'Nothing planned for this day yet.'));
     } else {
-      for (const entry of dayEntries) list.appendChild(entryRow(entry));
+      // Reordering only makes sense with 2+ entries — then each row gets a drag
+      // handle and dropping recomputes sort_order (see enableRowReorder).
+      const reorderable = dayEntries.length > 1;
+      const rows = [];
+      for (const entry of dayEntries) {
+        const { node, handle } = entryRow(entry, reorderable);
+        rows.push({ node, handle, entry });
+        list.appendChild(node);
+      }
+      if (reorderable) enableRowReorder(rows, () => tctx.refreshTrip());
     }
 
     mount(panel, header, list, formSection(dayEntries));
     panel.scrollTop = 0;
   }
 
-  function entryRow(entry) {
+  // Returns { node, handle } — handle is the drag grip (null unless reorderable).
+  function entryRow(entry, reorderable) {
     const info = typeInfo(entry.type);
     const time = formatTimeRange(entry.start_time, entry.end_time);
     const hasPrice = entry.price != null;
     const flight = hasSegments(entry);
-    return el(
+    const handle = reorderable
+      ? el('span', { class: 'entry-drag-handle', title: 'Drag to reorder', 'aria-hidden': 'true' }, '⋮⋮')
+      : null;
+    const node = el(
       'div',
       { class: 'entry-row', style: { '--chip': info.color } },
+      handle,
       el('span', { class: 'entry-icon' }, info.icon),
       el(
         'div',
@@ -142,6 +157,7 @@ export function openDayEditor(tctx, date) {
         el('button', { class: 'icon-btn danger', title: 'Delete', onClick: () => onDelete(entry) }, '🗑'),
       ),
     );
+    return { node, handle };
   }
 
   // "until 8 Aug · 3 days" for stays; "5 Aug 20:50 → 7 Aug 06:30" otherwise.