feat: optimize routes around accommodation, confirm note deletions (#1123)

Optimize day routes around the accommodation

When a day has an accommodation set, the route optimizer now treats it as
the day's home base: it optimizes a loop that leaves the hotel and returns
to it, so the stop nearest the hotel comes first. On a transfer day -
checking out of one hotel and into another - the route runs from the first
hotel to the second instead.

The optimizer also gained a 2-opt pass on top of the nearest-neighbor
ordering, which removes the crossings the greedy pass used to leave behind.
A new display setting ("optimize route from accommodation", on by default)
lets you turn the anchoring off.

Confirm before deleting notes

Deleting a plan note or a collab note now asks for confirmation first. On
phones and tablets the edit and delete icons sit close together and were
easy to mis-tap, which deleted notes with no way back.

client/src/utils/dayOrder.ts

@@ -1,8 +1,34 @@
-import type { Day } from '../types'
+import type { Day, Accommodation, RouteAnchors } from '../types'
 
 export const getDayOrder = (day: Day, days: Day[]): number =>
   day.day_number ?? days.indexOf(day)
 
+// Derives route anchors from the accommodation(s) active on a day. A single hotel is the day's home
+// base, so the route is a loop that starts and ends there. A transfer day — checking out of one hotel
+// and into another — instead runs from the morning hotel to the evening one.
+export const getAccommodationAnchors = (
+  day: Day,
+  days: Day[],
+  accommodations: Accommodation[],
+): RouteAnchors => {
+  const located = accommodations.filter(a =>
+    a.place_lat != null && a.place_lng != null &&
+    isDayInAccommodationRange(day, a.start_day_id, a.end_day_id, days),
+  )
+  if (located.length === 0) return {}
+
+  const toAnchor = (a: Accommodation) => ({ lat: a.place_lat as number, lng: a.place_lng as number })
+
+  const checkOut = located.find(a => a.end_day_id === day.id) // the hotel you leave this morning
+  const checkIn = located.find(a => a.start_day_id === day.id) // the hotel you arrive at tonight
+  if (checkOut && checkIn && checkOut !== checkIn) {
+    return { start: toAnchor(checkOut), end: toAnchor(checkIn) }
+  }
+
+  const hotel = toAnchor(located[0])
+  return { start: hotel, end: hotel }
+}
+
 export const isDayInAccommodationRange = (
   day: Day,
   startDayId: number,