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/compat/predicate/isSet.d.ts

@@ -0,0 +1,21 @@
+//#region src/compat/predicate/isSet.d.ts
+/**
+ * Checks if a given value is `Set`.
+ *
+ * This function can also serve as a type predicate in TypeScript, narrowing the type of the argument to `Set`.
+ *
+ * @param value The value to check if it is a `Set`.
+ * @returns Returns `true` if `value` is a `Set`, else `false`.
+ *
+ * @example
+ * const value1 = new Set();
+ * const value2 = new Map();
+ * const value3 = new WeakSet();
+ *
+ * console.log(isSet(value1)); // true
+ * console.log(isSet(value2)); // false
+ * console.log(isSet(value3)); // false
+ */
+declare function isSet(value?: any): value is Set<any>;
+//#endregion
+export { isSet };