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/function/identity.d.mts

@@ -0,0 +1,23 @@
+//#region src/function/identity.d.ts
+/**
+ * Returns the input value unchanged.
+ *
+ * @template T - The type of the input value.
+ * @param x - The value to be returned.
+ * @returns The input value.
+ *
+ * @example
+ * // Returns 5
+ * identity(5);
+ *
+ * @example
+ * // Returns 'hello'
+ * identity('hello');
+ *
+ * @example
+ * // Returns { key: 'value' }
+ * identity({ key: 'value' });
+ */
+declare function identity<T>(x: T): T;
+//#endregion
+export { identity };