feat(maps): draw every travel day's route at once, with the trip total

Extract the day route builder out of useRouteCalculation into a pure module and
aggregate it over the whole trip: one map with every day's route, each day in its
own colour, the mode per stage and the trip's total distance. Straight lines first,
roads as they answer; a refused leg keeps its line and adds no distance.

Give the floating map controls one shared drop shadow while adding the toggle, so
the new pill and the base-layer switcher stand off the tiles the way the locate
button always has. Document the control in wiki/Map-Features.md.

Addresses #1736

client/src/components/Map/mapControlShadow.ts

@@ -0,0 +1,10 @@
+/**
+ * The drop shadow every floating map control carries.
+ *
+ * Tighter and darker than `--sidebar-shadow`, which is built for a panel resting on
+ * the app background: over map tiles its 0.10 alpha spread over 32px all but
+ * disappears, so a round control read as painted onto the map rather than floating
+ * above it. This is the locate button's shadow, which was always the odd one out for
+ * exactly that reason — the others were the ones that needed to match it.
+ */
+export const MAP_CONTROL_SHADOW = '0 2px 10px rgba(0,0,0,0.25)'