feat(client): route every day through Valhalla where the TREK services or an own Valhalla answer

With the TREK services or an own Valhalla, the day plan, the road trip and
the other ways of a leg are routed by Valhalla on foot, by bike and by car,
twenty locations a request. A day it cannot answer (relay refusal, time out,
no way for a leg) goes to OSRM whole and without a word; it is never handed
to FOSSGIS unless it avoids something only Valhalla can avoid. With FOSSGIS
nothing changes: OSRM routes the days and Valhalla the avoidances.

A Valhalla answer is cached under its own key beside the OSRM one, so
switching engines never serves a day from the other engine. The Valhalla
day routing moves out of RouteCalculator into valhallaDayRoute.ts.

client/src/components/Map/routeText.ts

@@ -0,0 +1,27 @@
+import { useSettingsStore } from '../../store/settingsStore';
+import type { DistanceUnit } from '../../types';
+import { formatDistance } from '../../utils/units';
+
+/** The unit a route's texts are written in, which is why it is part of the route cache key. */
+export function getDistanceUnit(): DistanceUnit {
+  return useSettingsStore.getState().settings.distance_unit === 'imperial' ? 'imperial' : 'metric';
+}
+
+/** A routed distance as the connectors show it: metres below a kilometre, else the user's unit. */
+export function formatRouteDistance(meters: number): string {
+  const unit = getDistanceUnit();
+  if (unit === 'metric' && meters < 1000) {
+    return `${Math.round(meters)} m`;
+  }
+  return formatDistance(meters / 1000, unit);
+}
+
+/** A routed time in hours and minutes, the minutes rounded down. */
+export function formatDuration(seconds: number): string {
+  const h = Math.floor(seconds / 3600);
+  const m = Math.floor((seconds % 3600) / 60);
+  if (h > 0) {
+    return `${h} h ${m} min`;
+  }
+  return `${m} min`;
+}