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/composables/useClusteredNodes.ts

@@ -0,0 +1,48 @@
+import { GetClusteredNodesDocument } from './graphql/public/geo-generated'
+import type { ClusterPointType } from './graphql/public/geo-generated'
+
+export interface MapBounds {
+  west: number
+  south: number
+  east: number
+  north: number
+  zoom: number
+}
+
+export function useClusteredNodes(transportType?: Ref<string | undefined>) {
+  const { $geoClient } = useNuxtApp()
+
+  const clusteredNodes = ref<ClusterPointType[]>([])
+  const loading = ref(false)
+
+  const fetchClusters = async (bounds: MapBounds) => {
+    loading.value = true
+    try {
+      const { data } = await $geoClient.query({
+        query: GetClusteredNodesDocument,
+        variables: {
+          west: bounds.west,
+          south: bounds.south,
+          east: bounds.east,
+          north: bounds.north,
+          zoom: Math.floor(bounds.zoom),
+          transportType: transportType?.value
+        },
+        fetchPolicy: 'network-only'
+      })
+
+      clusteredNodes.value = (data?.clusteredNodes ?? []).filter(Boolean) as ClusterPointType[]
+    } catch (error) {
+      console.error('Failed to fetch clustered nodes:', error)
+      clusteredNodes.value = []
+    } finally {
+      loading.value = false
+    }
+  }
+
+  return {
+    clusteredNodes,
+    loading,
+    fetchClusters
+  }
+}