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/isPlainObject.d.mts

@@ -0,0 +1,26 @@
+//#region src/compat/predicate/isPlainObject.d.ts
+/**
+ * Checks if a given value is a plain object.
+ *
+ * A plain object is an object created by the `{}` literal, `new Object()`, or
+ * `Object.create(null)`.
+ *
+ * This function also handles objects with custom
+ * `Symbol.toStringTag` properties.
+ *
+ * `Symbol.toStringTag` is a built-in symbol that a constructor can use to customize the
+ * default string description of objects.
+ *
+ * @param [object] - The value to check.
+ * @returns True if the value is a plain object, otherwise false.
+ *
+ * @example
+ * console.log(isPlainObject({})); // true
+ * console.log(isPlainObject([])); // false
+ * console.log(isPlainObject(null)); // false
+ * console.log(isPlainObject(Object.create(null))); // true
+ * console.log(isPlainObject(new Map())); // false
+ */
+declare function isPlainObject(object?: any): boolean;
+//#endregion
+export { isPlainObject };