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.mjs

@@ -0,0 +1,39 @@
+//#region src/compat/predicate/isPlainObject.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
+*/
+function isPlainObject(object) {
+	if (typeof object !== "object") return false;
+	if (object == null) return false;
+	if (Object.getPrototypeOf(object) === null) return true;
+	if (Object.prototype.toString.call(object) !== "[object Object]") {
+		const tag = object[Symbol.toStringTag];
+		if (tag == null) return false;
+		if (!Object.getOwnPropertyDescriptor(object, Symbol.toStringTag)?.writable) return false;
+		return object.toString() === `[object ${tag}]`;
+	}
+	let proto = object;
+	while (Object.getPrototypeOf(proto) !== null) proto = Object.getPrototypeOf(proto);
+	return Object.getPrototypeOf(object) === proto;
+}
+//#endregion
+export { isPlainObject };