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/isNotNil.mjs

@@ -0,0 +1,22 @@
+//#region src/predicate/isNotNil.ts
+/**
+* Checks if the given value is not null nor undefined.
+*
+* The main use of this function is to be used with TypeScript as a type predicate.
+*
+* @template T - The type of value.
+* @param x - The value to test if it is not null nor undefined.
+* @returns True if the value is not null nor undefined, false otherwise.
+*
+* @example
+* // Here the type of `arr` is (number | undefined)[]
+* const arr = [1, undefined, 3];
+* // Here the type of `result` is number[]
+* const result = arr.filter(isNotNil);
+* // result will be [1, 3]
+*/
+function isNotNil(x) {
+	return x != null;
+}
+//#endregion
+export { isNotNil };