Always reset map pins when changing routes

Prior to this commit, we only reset all pins styling when changing
between artwork detail pages. This meant going back to the index page
didn’t reset them, leaving the last highlighted pin highlighted.

Now, we reset them whenever the route changes, which is what we intend.

Issue #103 Highlighted map pin doesn't reset when returning to search
           results

front-end/src/components/LeafletMap.vue

@@ -114,11 +114,11 @@ onMounted(() => {
 watch(
   () => route.params.id,
   (newId) => {
+    markerTable.forEach((marker) => {
+      marker.setIcon(defaultIcon);
+      marker.setZIndexOffset(0);
+    });
     if (newId) {
-      markerTable.forEach((marker) => {
-        marker.setIcon(defaultIcon);
-        marker.setZIndexOffset(0);
-      });
       const marker = markerTable.get(newId as string);
       if (marker) {
         marker.setIcon(activeIcon);