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/isSymbol.d.mts

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+//#region src/predicate/isSymbol.d.ts
+/**
+ * Check whether a value is a symbol.
+ *
+ * This function can also serve as a type predicate in TypeScript, narrowing the type of the argument to `symbol`.
+ *
+ * @param value The value to check.
+ * @returns Returns `true` if `value` is a symbol, else `false`.
+ *
+ * @example
+ * import { isSymbol } from 'es-toolkit/predicate';
+ *
+ * isSymbol(Symbol('a')); // true
+ * isSymbol(Symbol.for('a')); // true
+ * isSymbol(Symbol.iterator); // true
+ *
+ * isSymbol(null); // false
+ * isSymbol(undefined); // false
+ * isSymbol('123'); // false
+ * isSymbol(false); // false
+ * isSymbol(123n); // false
+ * isSymbol({}); // false
+ * isSymbol([1, 2, 3]); // false
+ */
+declare function isSymbol(value: unknown): value is symbol;
+//#endregion
+export { isSymbol };