Apply the NPS-inspired palette to the online map too

ONLINE_STYLE_PATCH mirrors OFFLINE_THEME's color choices onto
OpenFreeMap Liberty's OpenMapTiles layer ids (a separate hand-built
table -- the two schemas share no layer names). loadOnlineStyle
fetches Liberty's style.json once, patches it in place, and the
result replaces the plain URL everywhere ONLINE_STYLE is used --
MapLibre accepts a style object anywhere it accepts a style URL, so
applyStyle needed no change.

Runs before the map (and the rest of the page) is constructed, so
there's no flash of Liberty's own colors first -- but with a 3s
timeout and a catch-all fallback to the plain URL, since this app is
meant to keep working offline in the field and blocking startup on a
remote style server would undermine that.

Verified in a real browser: online map now visually matches the
offline theme (cream ground, brown/khaki land cover, green parks,
muted roads), no console errors, Online/Offline toggle still works.

docs/nps-resources.adoc

@@ -24,8 +24,8 @@ checking here before searching from zero next time.
 | MIT (per `package.json`); the whole `npmap5-plugins` repo is separately
   public domain as a US government work
 
-| Park Tiles color palette (offline basemap theme)
-| `public/js/map.js`'s `OFFLINE_THEME`
+| Park Tiles color palette (offline + online basemap themes)
+| `public/js/map.js`'s `OFFLINE_THEME` and `ONLINE_STYLE_PATCH`
 | Colors only — see <<park-tiles>> for why the actual tile service isn't used
 
 | `overview` (top-right minimap/inset control)