Add a Hiking trails overlay (Waymarked Trails, online only)

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.

public/js/icons.js

@@ -328,7 +328,11 @@ const FISHING_ICON = `
 const SCENIC_VIEWPOINT_ICON = `
 <svg viewBox="0 0 22 22" fill="currentColor"><g transform="translate(4.000000, 0.000000)"><path d="M3.2,11c0,1.2-0.9,2.2-2.1,2.2c-1.2,0-2.1-1-2.1-2.2 c0-1.2,0.9-2.2,2.1-2.2C2.2,8.8,3.2,9.8,3.2,11"/><path d="M4.6,10.4v1.3l10.6,0.8v-3L4.6,10.4"/><path d="M2.3,7.5l1.1,0.7L7.7,2L5.3,0.5L2.3,7.5"/><path d="M4.4,9.8l7.9-3.8l-1.4-2.6L3.8,8.6L4.4,9.8z"/><path d="M2.3,14.5l1.1-0.7l4.3,6.2l-2.4,1.5L2.3,14.5"/><path d="M3.8,13.4l0.6-1.2l7.9,3.8l-1.4,2.6L3.8,13.4"/></g></svg>`;
 
-const WALKING_ICON = `
+// Exported (unlike the other POI glyphs around it) — also used as the
+// Overlays panel's Hiking trails glyph (hiking_trails.js), same "reuse an
+// existing NPS-sourced pictogram" story as WILDERNESS_ICON above rather
+// than hand-drawing another one.
+export const WALKING_ICON = `
 <svg viewBox="0 0 22 22" fill="currentColor"><path d="M10.4,3.6c1,0,1.8-0.8,1.7-1.8c0-1-0.8-1.8-1.8-1.7c-1,0-1.8,0.8-1.7,1.8C8.6,2.8,9.5,3.6,10.4,3.6z"/><path d="M16.5,9.5L13.9,8l-2.2-3.4c-0.3-0.4-0.9-0.8-1.5-0.7C9.7,4,9.3,4.2,9,4.4L5.8,7.7C5.7,7.8,5.6,8,5.6,8.1l-0.4,3.6 c0,0,0,0.1,0,0.1c0,0.4,0.4,0.8,0.8,0.8c0.4,0,0.7-0.4,0.8-0.8l0.3-3.1l1.1-1.1l-1,8.6l-1.9,4.1c-0.1,0.1-0.1,0.3-0.1,0.5 c0,0.7,0.6,1.2,1.2,1.2c0.5,0,0.9-0.3,1.1-0.7l2-4.4c0-0.1,0.2-0.4,0.2-0.5l0.2-2.1l2.1,6.9c0.2,0.5,0.6,0.8,1.2,0.8 c0.7,0,1.2-0.6,1.2-1.2c0-0.1,0-0.1,0-0.2L11.5,11l0.4-3.1l0.8,1.3c0.1,0.1,0.1,0.2,0.2,0.2l2.8,1.6c0.1,0,0.2,0.1,0.4,0.1 c0.4,0,0.8-0.4,0.8-0.8C16.9,9.8,16.7,9.6,16.5,9.5z"/></svg>`;
 
 const GUIDED_TOURS_ICON = `