refactor: export infrastructure layers with explicit application callbacks

src/data/infrastructure.js

@@ -0,0 +1,38 @@
+import { createLocalGeoJsonLayer } from './localGeojsonCore.js';
+
+// Resolved by Vite in builds and relative to this module in other consumers.
+const datacentersUrl = new URL('./local_data/datacenters/datacenters.geojsonl', import.meta.url).href;
+const damsUrl = new URL('./local_data/dams/dams.geojsonl', import.meta.url).href;
+
+/**
+ * Create fresh datacenter and dam layers without starting or loading them.
+ * @param {object} services Caller-owned context, overlay and render operations.
+ * @returns {object[]} Datacenters then dams, with stable standalone identities.
+ */
+export function createInfrastructureLayers(services) {
+  const datacenters = createLocalGeoJsonLayer({
+    id: 'local-datacenters',
+    url: datacentersUrl,
+    name: 'Datacenters',
+    color: '#00ffff', // Cyan
+    icon: '▣',
+    source: 'Local',
+    labels: true,
+    labelMax: 700,
+    labelGridPx: 138,
+  }, services);
+
+  const dams = createLocalGeoJsonLayer({
+    id: 'local-dams',
+    url: damsUrl,
+    name: 'Dams',
+    color: '#0088ff', // Blue
+    icon: '▰',
+    source: 'USACE',
+    labels: true,
+    labelMax: 900,
+    labelGridPx: 132,
+  }, services);
+
+  return [datacenters, dams];
+}