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/flatten.mjs

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+//#region src/array/flatten.ts
+/**
+* Flattens an array up to the specified depth.
+*
+* @template T - The type of elements within the array.
+* @template D - The depth to which the array should be flattened.
+* @param arr - The array to flatten.
+* @param depth - The depth level specifying how deep a nested array structure should be flattened. Defaults to 1.
+* @returns A new array that has been flattened.
+*
+* @example
+* const arr = flatten([1, [2, 3], [4, [5, 6]]], 1);
+* // Returns: [1, 2, 3, 4, [5, 6]]
+*
+* const arr = flatten([1, [2, 3], [4, [5, 6]]], 2);
+* // Returns: [1, 2, 3, 4, 5, 6]
+*/
+function flatten(arr, depth = 1) {
+	const result = [];
+	const flooredDepth = Math.floor(depth);
+	const recursive = (arr, currentDepth) => {
+		for (let i = 0; i < arr.length; i++) {
+			const item = arr[i];
+			if (Array.isArray(item) && currentDepth < flooredDepth) recursive(item, currentDepth + 1);
+			else result.push(item);
+		}
+	};
+	recursive(arr, 0);
+	return result;
+}
+//#endregion
+export { flatten };