feat: pin the fastest point on the trip replay map (FEAT-16)

When a route loads, add an amber circle + permanent 'Max speed: X km/h'
tooltip at the point with the highest speed. Shared history.js, so it
applies to both the Pi and the server portal.

static/js/history.js

@@ -172,6 +172,24 @@
                 L.marker(coords[0]).bindPopup("Start").addTo(st.route);
                 L.marker(coords[coords.length - 1]).bindPopup("End").addTo(st.route);
             }
+            // Pin the fastest point on the route.
+            var maxPt = null;
+            for (var i = 0; i < d.points.length; i++) {
+                if (!maxPt || d.points[i].speed > maxPt.speed) maxPt = d.points[i];
+            }
+            if (maxPt && maxPt.speed > 0) {
+                L.circleMarker([maxPt.latitude, maxPt.longitude], {
+                    radius: 6,
+                    color: "#fff",
+                    weight: 2,
+                    fillColor: "#f6c23e",
+                    fillOpacity: 1,
+                })
+                .bindTooltip("Max speed: " + fS(maxPt.speed), {
+                    permanent: true, direction: "top", offset: [0, -8],
+                })
+                .addTo(st.route);
+            }
             st.route.addTo(map);
             if (sig.aborted) { cleanup(); return; }
             if (coords.length > 1) map.fitBounds(st.route.getBounds(), {padding: [24, 24], maxZoom: 15});