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/isNil.d.mts

@@ -0,0 +1,23 @@
+//#region src/compat/predicate/isNil.d.ts
+/**
+ * Checks if a given value is null or undefined.
+ *
+ * This function tests whether the provided value is either `null` or `undefined`.
+ * It returns `true` if the value is `null` or `undefined`, and `false` otherwise.
+ *
+ * This function can also serve as a type predicate in TypeScript, narrowing the type of the argument to `null` or `undefined`.
+ *
+ * @param x - The value to test for null or undefined.
+ * @returns `true` if the value is null or undefined, `false` otherwise.
+ *
+ * @example
+ * const value1 = null;
+ * const value2 = undefined;
+ * const value3 = 42;
+ * const result1 = isNil(value1); // true
+ * const result2 = isNil(value2); // true
+ * const result3 = isNil(value3); // false
+ */
+declare function isNil(x: any): x is null | undefined;
+//#endregion
+export { isNil };