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/set/countBy.d.ts

@@ -0,0 +1,27 @@
+//#region src/set/countBy.d.ts
+/**
+ * Counts the occurrences of items in a Set based on a transformation function.
+ *
+ * This function takes a Set and a function that generates a key from each value.
+ * It returns a Map with the generated keys and their counts as values.
+ * The count is incremented for each element for which the transformation produces the same key.
+ *
+ * @template T - The type of elements in the Set.
+ * @template K - The type of keys produced by the transformation function.
+ * @param set - The Set to count occurrences from.
+ * @param mapper - The function to produce a key for counting.
+ * @returns A Map containing the mapped keys and their counts.
+ *
+ * @example
+ * const set = new Set([1, 2, 3, 4, 5]);
+ * const result = countBy(set, (value) => value % 2 === 0 ? 'even' : 'odd');
+ * // result will be Map(2) { 'odd' => 3, 'even' => 2 }
+ *
+ * @example
+ * const set = new Set(['apple', 'banana', 'cherry']);
+ * const result = countBy(set, (value) => value.length);
+ * // result will be Map(2) { 5 => 1, 6 => 2 }
+ */
+declare function countBy<T, K>(set: Set<T>, mapper: (value: T, value2: T, set: Set<T>) => K): Map<K, number>;
+//#endregion
+export { countBy };