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/util/toString.js

@@ -0,0 +1,27 @@
+//#region src/compat/util/toString.ts
+/**
+* Converts `value` to a string.
+*
+* An empty string is returned for `null` and `undefined` values.
+* The sign of `-0` is preserved.
+*
+* @param value - The value to convert.
+* @returns Returns the converted string.
+*
+* @example
+* toString(null) // returns ''
+* toString(undefined) // returns ''
+* toString(-0) // returns '-0'
+* toString([1, 2, -0]) // returns '1,2,-0'
+* toString([Symbol('a'), Symbol('b')]) // returns 'Symbol(a),Symbol(b)'
+*/
+function toString(value) {
+	if (value == null) return "";
+	if (typeof value === "string") return value;
+	if (Array.isArray(value)) return value.map(toString).join(",");
+	const result = String(value);
+	if (result === "0" && Object.is(Number(value), -0)) return "-0";
+	return result;
+}
+//#endregion
+exports.toString = toString;