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/array/flatMapAsync.mjs

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+import { limitAsync } from "./limitAsync.mjs";
+import { flatten } from "./flatten.mjs";
+//#region src/array/flatMapAsync.ts
+/**
+* Maps each element in an array using an async callback function and flattens the result by one level.
+*
+* This is equivalent to calling `mapAsync` followed by `flat(1)`, but more efficient.
+* Each callback should return an array, and all returned arrays are concatenated into
+* a single output array.
+*
+* @template T - The type of elements in the input array.
+* @template R - The type of elements in the arrays returned by the callback.
+* @param array The array to transform.
+* @param callback An async function that transforms each element into an array.
+* @param [options] Optional configuration object.
+* @param [options.concurrency] Maximum number of concurrent async operations. If not specified, all operations run concurrently.
+* @returns A promise that resolves to a flattened array of transformed values.
+* @example
+* const users = [{ id: 1 }, { id: 2 }];
+* const allPosts = await flatMapAsync(users, async (user) => {
+*   return await fetchUserPosts(user.id);
+* });
+* // Returns: [post1, post2, post3, ...] (all posts from all users)
+*
+* @example
+* // With concurrency limit
+* const numbers = [1, 2, 3];
+* const results = await flatMapAsync(
+*   numbers,
+*   async (n) => await fetchRelatedItems(n),
+*   { concurrency: 2 }
+* );
+* // Processes at most 2 operations concurrently
+*/
+async function flatMapAsync(array, callback, options) {
+	if (options?.concurrency != null) callback = limitAsync(callback, options.concurrency);
+	return flatten(await Promise.all(array.map(callback)));
+}
+//#endregion
+export { flatMapAsync };