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

graphql/operations/public/geo/GetClusteredNodes.graphql

@@ -0,0 +1,24 @@
+query GetClusteredNodes(
+  $west: Float!
+  $south: Float!
+  $east: Float!
+  $north: Float!
+  $zoom: Int!
+  $transportType: String
+) {
+  clusteredNodes(
+    west: $west
+    south: $south
+    east: $east
+    north: $north
+    zoom: $zoom
+    transportType: $transportType
+  ) {
+    id
+    latitude
+    longitude
+    count
+    expansionZoom
+    name
+  }
+}