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/fp/array/flattenDeep.d.mts

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+import { ExtractNestedArrayType } from "../../array/flattenDeep.mjs";
+
+//#region src/fp/array/flattenDeep.d.ts
+/**
+ * Creates a function that recursively flattens an array.
+ *
+ * The returned function is lazy-capable inside {@link pipe}. A trailing
+ * short-circuiting operator can stop before later nested values are visited.
+ *
+ * @template T - The type of elements in the array.
+ * @returns A function that maps the piped array to a deeply flattened array.
+ *
+ * @example
+ * import { flattenDeep, pipe } from 'es-toolkit/fp';
+ *
+ * pipe([1, [2, [3]]], flattenDeep());
+ * // => [1, 2, 3]
+ */
+declare function flattenDeep<T>(): (array: readonly T[]) => Array<ExtractNestedArrayType<T>>;
+//#endregion
+export { flattenDeep };