Add settings page for managing forecasting API key and URL via UI

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/node_modules/recharts/es6/context/legendPayloadContext.js

@@ -0,0 +1,10 @@
+import { useAppSelector } from '../state/hooks';
+import { selectLegendPayload } from '../state/selectors/legendSelectors';
+
+/**
+ * Use this hook in Legend, or anywhere else where you want to read the current Legend items.
+ * @return all Legend items ready to be rendered
+ */
+export function useLegendPayload() {
+  return useAppSelector(selectLegendPayload);
+}