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/array/at.d.mts

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+//#region src/array/at.d.ts
+/**
+ * Retrieves elements from an array at the specified indices.
+ *
+ * This function supports negative indices, which count from the end of the array.
+ *
+ * @template T
+ * @param arr - The array to retrieve elements from.
+ * @param indices - An array of indices specifying the positions of elements to retrieve.
+ * @returns A new array containing the elements at the specified indices.
+ *
+ * @example
+ * const numbers = [10, 20, 30, 40, 50];
+ * const result = at(numbers, [1, 3, 4]);
+ * console.log(result); // [20, 40, 50]
+ */
+declare function at<T>(arr: readonly T[], indices: number[]): T[];
+//#endregion
+export { at };