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/predicate/isDate.d.mts

@@ -0,0 +1,17 @@
+//#region src/predicate/isDate.d.ts
+/**
+ * Checks if `value` is a Date object.
+ *
+ * @param value The value to check.
+ * @returns Returns `true` if `value` is a Date object, `false` otherwise.
+ *
+ * @example
+ * const value1 = new Date();
+ * const value2 = '2024-01-01';
+ *
+ * console.log(isDate(value1)); // true
+ * console.log(isDate(value2)); // false
+ */
+declare function isDate(value: unknown): value is Date;
+//#endregion
+export { isDate };