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/workbox-routing/setDefaultHandler.d.ts

@@ -0,0 +1,16 @@
+import { RouteHandler } from 'workbox-core/types.js';
+import './_version.js';
+/**
+ * Define a default `handler` that's called when no routes explicitly
+ * match the incoming request.
+ *
+ * Without a default handler, unmatched requests will go against the
+ * network as if there were no service worker present.
+ *
+ * @param {workbox-routing~handlerCallback} handler A callback
+ * function that returns a Promise resulting in a Response.
+ *
+ * @memberof workbox-routing
+ */
+declare function setDefaultHandler(handler: RouteHandler): void;
+export { setDefaultHandler };