New Overlays panel toggle, same plain on/off shape as Contour lines —
raster tiles from waymarkedtrails.org, which already color each route
by its OSM colour tag (the KST/KČT paint-blaze colors used in
Slovakia/Czechia, plain red elsewhere), so no styling work needed here.
Online only for now; offline (baked into offline.pmtiles) needs a
custom Planetiler profile for route relations, deferred until there's
a route planner/router to pair it with.
