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/math/percentile.d.ts

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+//#region src/math/percentile.d.ts
+/**
+ * Calculates the value at the given percentile of an array of numbers.
+ *
+ * Sorts the array in ascending order and returns the element at the nearest rank.
+ * See {@link https://en.wikipedia.org/wiki/Percentile#The_nearest-rank_method | Nearest rank method}.
+ *
+ * `NaN` values are sorted as the smallest values. Returns `NaN` if the array is empty.
+ *
+ * @param arr - An array of numbers to calculate the percentile.
+ * @param percentile - The percentile to compute, in the range `[0, 100]`.
+ * @returns The value at the given percentile.
+ * @throws {Error} Throws an error if `percentile` is not a number, less than `0`, or greater than `100`.
+ *
+ * @example
+ * percentile([1, 2, 3, 4, 5], 50);
+ * // Returns 3
+ *
+ * @example
+ * percentile([1, 2, 3, 4, 5], 75);
+ * // Returns 4
+ *
+ * @example
+ * percentile([5, 1, 4, 2, 3], 0);
+ * // Returns 1
+ */
+declare function percentile(arr: readonly number[], percentile: number): number;
+//#endregion
+export { percentile };