Explore places on the map, planner route fixes, and instance-wide Mapbox (#1147)

* feat(maps): add an OSM POI search endpoint (category within a viewport)

New /api/maps/pois queries OpenStreetMap via Overpass for places of a category
(restaurants, cafes, hotels, sights, …) inside a bounding box. OSM-only by design
— it never calls Google, even when a Google key is configured.

* feat(map): explore nearby places on the trip map (OSM category pill)

A floating, icon-only pill over the planner map lets you toggle a POI category and
see those OpenStreetMap places in the current view; clicking a marker opens the
add-place form pre-filled (name, address, website, phone). Single-select with a
'search this area' action after the map moves. Renders on both the Leaflet and
Mapbox maps, and can be turned off in settings (discussion #841).

* fix(planner): anchor timed places when optimising and route transports by location

- The day optimiser no longer reshuffles places that have a set time — they stay
  anchored to their time, like locked places.
- The route now uses a transport's departure/arrival location as a waypoint when it
  has one (e.g. a flight's airport), instead of breaking the route at every booking;
  transports without a location are ignored for routing but still show their leg's
  distance/duration under the booking.

* feat(admin): instance-wide Mapbox defaults in default user settings

Admins can set a shared Mapbox token (plus style, 3D and quality) as instance
defaults, so the whole instance can use Mapbox without each user pasting their own
key. Users without their own value inherit it via the existing admin-defaults
merge; the shared token is stored encrypted (discussion #920).

shared/src/i18n/nl/admin.ts

@@ -379,5 +379,15 @@ const admin: TranslationStrings = {
     'Verwijder alle passkeys van deze gebruiker (bijv. bij een verloren apparaat). Ze kunnen nog steeds inloggen met hun wachtwoord.',
   'admin.passkey.resetConfirm': 'Alle passkeys voor {name} verwijderen?',
   'admin.passkey.resetDone': '{count} passkey(s) verwijderd',
+  'admin.defaultSettings.mapProvider': 'Kaartmotor',
+  'admin.defaultSettings.mapProviderHint': 'De standaardkaart voor iedereen op deze instantie. Elke gebruiker kan dit nog steeds aanpassen in zijn eigen instellingen.',
+  'admin.defaultSettings.providerLeaflet': 'Standaard (gratis)',
+  'admin.defaultSettings.providerMapbox': 'Mapbox (3D)',
+  'admin.defaultSettings.mapboxToken': 'Gedeeld Mapbox-token',
+  'admin.defaultSettings.mapboxTokenHint': 'Wordt gebruikt voor elke gebruiker die nog geen eigen token heeft ingevoerd — zo krijgt de hele instantie Mapbox zonder de sleutel apart te delen. Versleuteld opgeslagen.',
+  'admin.defaultSettings.mapboxStyle': 'Kaartstijl',
+  'admin.defaultSettings.mapboxStylePlaceholder': 'Kies een stijl…',
+  'admin.defaultSettings.mapbox3d': '3D-gebouwen & terrein',
+  'admin.defaultSettings.mapboxQuality': 'Hogekwaliteitsmodus',
 };
 export default admin;