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/flatMap.d.ts

@@ -0,0 +1,28 @@
+//#region src/fp/array/flatMap.d.ts
+/**
+ * Creates a function that maps every element to an array with `callback` and
+ * concatenates the results, equivalent to `Array.prototype.flatMap`. Use it
+ * with {@link pipe}.
+ *
+ * The returned function is **lazy-capable**: inside a {@link pipe} it is fused
+ * with adjacent lazy functions and runs element-by-element, so a trailing
+ * `take` can terminate the walk early without expanding the rest of the input.
+ *
+ * @template T - The type of elements in the input array.
+ * @template U - The type of elements in the output array.
+ * @param callback - Called with `(value, index)` for each element; returns an
+ *   array whose elements are flattened into the output.
+ * @returns A function that maps a `readonly T[]` to a new `U[]`.
+ *
+ * @example
+ * import { pipe, flatMap } from 'es-toolkit/fp';
+ *
+ * pipe([1, 2, 3], flatMap(x => [x, x * 10])); // => [1, 10, 2, 20, 3, 30]
+ *
+ * @example
+ * // Returning an empty array drops the element.
+ * pipe([1, 2, 3, 4], flatMap(x => (x % 2 === 0 ? [x] : []))); // => [2, 4]
+ */
+declare function flatMap<T, U>(callback: (value: T, index: number) => U[]): (array: readonly T[]) => U[];
+//#endregion
+export { flatMap };