Rework entry types: merge hotel into stay, transport with modes, auto-transport

- Type set is now activity/stay/transport/flight/rental/note; hotel, travel
  and immigration are removed with idempotent startup data migrations
  (hotel->stay, travel->transport, immigration->activity with flag prefix)
- Transport entries carry an optional mode (train/bus/ferry/taxi/drive/other)
  that drives the chip/map icon; route stops expose transport_mode
- Creating a stay auto-creates a bridging transport to its neighbouring
  stays unless a transport/flight already covers the gap (one-shot)
- Summary: transports count replaces hotels/travelLegs

public/js/views/calendar.js

@@ -5,6 +5,7 @@ import { el } from '../dom.js';
 import {
   ENTRY_TYPES,
   typeInfo,
+  entryIcon,
   parseYMD,
   ymd,
   addDays,
@@ -189,7 +190,7 @@ function chip(entry, currency) {
       style: { '--chip': info.color },
       title: `${info.label}: ${chain ? `${entry.title} (${chain})` : entry.title}${hasPrice ? ` · ${formatMoney(entry.price, currency, { compact: true })}` : ''}`,
     },
-    el('span', { class: 'chip-icon' }, info.icon),
+    el('span', { class: 'chip-icon' }, entryIcon(entry)),
     el('span', { class: 'chip-text' }, label),
     hasPrice
       ? el('span', { class: 'chip-price' }, formatMoney(entry.price, currency, { compact: true }))
@@ -239,7 +240,7 @@ function dropoffChip(entry, tctx) {
       tabindex: '0',
       title: `Rental dropoff${car ? `: ${car}` : ''} — opens the pickup day`,
     },
-    el('span', { class: 'chip-icon' }, info.icon),
+    el('span', { class: 'chip-icon' }, entryIcon(entry)),
     el('span', { class: 'chip-text' }, 'dropoff'),
   );
   const open = (e) => { e.stopPropagation(); tctx.openDay(entry.date); };