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/es-toolkit/dist/compat/util/constant.mjs

@@ -0,0 +1,20 @@
+//#region src/compat/util/constant.ts
+/**
+* Creates a new function that always returns `value`.
+*
+* @template T - The type of the value to return.
+* @param value - The value to return from the new function.
+* @returns Returns the new constant function.
+*
+* @example
+* const object = { a: 1 };
+* const returnsObject = constant(object);
+*
+* returnsObject(); // => { a: 1 }
+* returnsObject() === object; // => true
+*/
+function constant(value) {
+	return () => value;
+}
+//#endregion
+export { constant };