SavedRouteID, when set, makes the worker load locations/costing/parameters
from routing.routes instead of trusting the body — used by the "export a
saved route" path. When empty the body's Locations/Costing/Parameters are
used (the dynamic, possibly-unsaved route currently on the map).

TeamID scopes the saved-route load to the caller's team. It is always set
by the handler from the authenticated context (never trusted from the
request body) so a SavedRouteID export can't cross team boundaries.