Note OpenTopoMap-style forest/meadow fill patterns as a TODO idea

TODO.adoc

@@ -30,6 +30,7 @@ independence from connectivity.
 ** [x] Filter panel as a "Unigrid Matrix" — an icon grid to toggle categories on/off, styled like the legend on an official NPS paper map, instead of plain dropdowns
 * [ ] Custom vector style (MVT/MapLibre) using the NPS color palette — muted natural tones for forests, water, and contours — so POIs and routes stand out at high zoom
 ** [ ] Landuse & protections: distinct styling for national parks, nature reserves (translucent green/gray-green), military zones, and private land (important for wild camping)
+** [ ] OpenTopoMap-style `fill-pattern` texture for forest (tree icons) and meadow/pasture (grass texture) landcover, instead of flat fill colors — Liberty's own sprite (`public/vendor/liberty-sprite/`) only has a `wetland` dot pattern, no tree/grass, so this needs custom pattern images added to the sprite sheet; works offline and online alike since it's just a style/sprite change, unlike pulling in OpenTopoMap's own raster tiles (online-only, restrictive tile-usage policy, wouldn't match the NPS palette)
 ** [x] Elevation-tinted terrain — a `color-relief` layer (hypsometric tint, this app's own green→brown→gray palette) under the hillshade layer, same "Terrain shading" toggle
 ** [x] Road hierarchy: clearly distinguish paved roads from unpaved/gravel/track — critical for knowing if the camper can get there