feat: add geolocate control to show user location on map

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: 2 people

src/where_the_plow/static/index.html

@@ -216,6 +216,13 @@ <h3>Where the Plow</h3>
       zoom: 12,
     });
 
+    const geolocate = new maplibregl.GeolocateControl({
+      positionOptions: { enableHighAccuracy: true },
+      trackUserLocation: true,
+      showUserHeading: true,
+    });
+    map.addControl(geolocate, 'bottom-right');
+
     function formatTimestamp(ts) {
       const d = new Date(ts);
       return d.toLocaleString(undefined, {