Home button fits all of Slovakia; add an overview map, top-right

Home now fitBounds()s a country-wide bbox instead of resetting to
CENTER/ZOOM's Bratislava point, since Home resetting into the same
city you'd already be looking at wasn't useful.

The overview map is NPS's own overview plugin (npmap5-plugins, still
on an unmerged branch), vendored and converted from its UMD dist
build to a plain ES module. Patched one MapLibre API break found while
verifying it: the plugin reads map.transform (public in the MapLibre
~2.4 it targets) to relax the inset's polar pan limit; MapLibre 6 (this
app's vendored version) no longer exposes .transform at all, so it
threw on load. Guarded to skip that cosmetic adjustment when absent
instead.

public/css/style.css

@@ -472,6 +472,12 @@ html, body {
   word-break: break-word;
 }
 
+.maplibregl-ctrl-overview-map {
+  border-radius: 4px;
+  overflow: hidden;
+  box-shadow: 0 0 0 2px rgba(0, 0, 0, 0.1);
+}
+
 .measure-ctrl {
   position: relative;
 }