remove route_calculation setting, always use OSRM routing (#1064)

The per-user route_calculation toggle was a second, hidden on/off layer
on top of the day footer's show-route button, and made it easy to end up
with straight-line routes for no obvious reason. Drop the setting
entirely: routing is always on, the footer toggle stays the single
switch. Old stored values are simply ignored (settings are key-value, no
migration needed).

client/tests/helpers/factories.ts

@@ -258,7 +258,6 @@ export function buildSettings(overrides: Partial<Settings> = {}): Settings {
     temperature_unit: 'fahrenheit',
     time_format: '12h',
     show_place_description: false,
-    route_calculation: false,
     blur_booking_codes: false,
     ...overrides,
   };