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/array/flattenDeep.d.ts

@@ -0,0 +1,17 @@
+import { ListOfRecursiveArraysOrValues } from "../_internal/ListOfRecursiveArraysOrValues.js";
+
+//#region src/compat/array/flattenDeep.d.ts
+/**
+ * Recursively flattens array.
+ *
+ * @template T
+ * @param array - The array to flatten.
+ * @returns Returns the new flattened array.
+ *
+ * @example
+ * flattenDeep([1, [2, [3, [4]], 5]]);
+ * // => [1, 2, 3, 4, 5]
+ */
+declare function flattenDeep<T>(value: ListOfRecursiveArraysOrValues<T> | null | undefined): Array<T extends string ? T : T extends ArrayLike<any> ? never : T>;
+//#endregion
+export { flattenDeep };