feat(map): add server-side h3 clustering and hover highlight

- Add useClusteredNodes composable for fetching clustered nodes
- Update CatalogMap to support server-side clustering mode
- Add bounds-change event for fetching clusters on map move/zoom
- Add hover event to HubCard for marker highlighting
- Update hubs/map page to use new clustering system

app/components/catalog/HubCard.vue

@@ -5,6 +5,8 @@
     class="block"
     :class="{ 'cursor-pointer': selectable }"
     @click="selectable && $emit('select')"
+    @mouseenter="$emit('hover', true)"
+    @mouseleave="$emit('hover', false)"
   >
     <Card
       padding="small"
@@ -49,6 +51,7 @@ const props = defineProps<{
 
 defineEmits<{
   (e: 'select'): void
+  (e: 'hover', hovered: boolean): void
 }>()
 
 const localePath = useLocalePath()