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/countBy.d.mts

@@ -0,0 +1,21 @@
+//#region src/fp/array/countBy.d.ts
+/**
+ * Creates a function that counts values by a derived key.
+ *
+ * The mapper receives each value, its index, and the full input array. The returned object
+ * uses mapper results as keys and occurrence counts as values.
+ *
+ * @template T - The type of elements in the array.
+ * @template K - The property-key type produced by the mapper.
+ * @param mapper - Called with each value, index, and array to produce a key.
+ * @returns A function that maps a readonly array to counts by key.
+ *
+ * @example
+ * import { countBy, pipe } from 'es-toolkit/fp';
+ *
+ * pipe([1, 2, 3, 4, 5], countBy(value => (value % 2 === 0 ? 'even' : 'odd')));
+ * // => { odd: 3, even: 2 }
+ */
+declare function countBy<T, K extends PropertyKey>(mapper: (item: T, index: number, array: readonly T[]) => K): (array: readonly T[]) => Record<K, number>;
+//#endregion
+export { countBy };