fix(web): add shared DemSource singleton, add ErrorBoundary, and conditional view rendering to prevent WebGL crash

apps/web/src/utils/demSource.ts

@@ -0,0 +1,27 @@
+import maplibregl from 'maplibre-gl';
+import mlcontour from 'maplibre-contour';
+
+let sharedDemSource: any = null;
+let isConfigured = false;
+
+export function getSharedDemSource() {
+  if (!sharedDemSource) {
+    sharedDemSource = new mlcontour.DemSource({
+      url: 'https://s3.amazonaws.com/elevation-tiles-prod/terrarium/{z}/{x}/{y}.png',
+      encoding: 'terrarium',
+      maxzoom: 15,
+      worker: true,
+      cacheSize: 100,
+    });
+
+    if (!isConfigured) {
+      try {
+        sharedDemSource.setupMaplibre(maplibregl);
+        isConfigured = true;
+      } catch (e) {
+        console.warn('DemSource setup warning:', e);
+      }
+    }
+  }
+  return sharedDemSource;
+}