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/isEmptyObject.d.ts

@@ -0,0 +1,16 @@
+//#region src/predicate/isEmptyObject.d.ts
+/**
+ * Checks if a value is an empty plain object.
+ *
+ * @param value - The value to check.
+ * @returns True if the value is an empty plain object, otherwise false.
+ *
+ * @example
+ * isEmptyObject({}); // true
+ * isEmptyObject({ a: 1 }); // false
+ * isEmptyObject([]); // false
+ * isEmptyObject(null); // false
+ */
+declare function isEmptyObject(value: unknown): value is Record<PropertyKey, never>;
+//#endregion
+export { isEmptyObject };