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/countBy.d.mts

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+//#region src/array/countBy.d.ts
+/**
+ * Count the occurrences of each item in an array
+ * based on a transformation function.
+ *
+ * This function takes an array and a transformation function
+ * that converts each item in the array to a key. It then
+ * counts the occurrences of each transformed item and returns
+ * an object with the transformed items as keys and the counts
+ * as values.
+ *
+ * @template T - The type of the items in the input array.
+ * @template K - The type of keys.
+ * @param arr - The input array to count occurrences.
+ * @param mapper - The transformation function that maps each item, its index, and the array to a key.
+ * @returns An object containing the transformed items as keys and the
+ * counts as values.
+ *
+ * @example
+ * const array = ['a', 'b', 'c', 'a', 'b', 'a'];
+ * const result = countBy(array, x => x);
+ * // result will be { a: 3, b: 2, c: 1 }
+ *
+ * @example
+ * const array = [1, 2, 3, 4, 5];
+ * const result = countBy(array, item => item % 2 === 0 ? 'even' : 'odd');
+ * // result will be { odd: 3, even: 2 }
+ *
+ * @example
+ * // Using index parameter
+ * const array = ['a', 'b', 'c', 'd'];
+ * const result = countBy(array, (item, index) => index < 2 ? 'first' : 'rest');
+ * // result will be { first: 2, rest: 2 }
+ */
+declare function countBy<T, K extends PropertyKey>(arr: readonly T[], mapper: (item: T, index: number, array: readonly T[]) => K): Record<K, number>;
+//#endregion
+export { countBy };