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-abstract/2018/abs.js

@@ -0,0 +1,9 @@
+'use strict';
+
+var $abs = require('math-intrinsics/abs');
+
+// https://262.ecma-international.org/5.1/#sec-5.2
+
+module.exports = function abs(x) {
+	return $abs(x);
+};