client/src/store/useAppStore.ts

import { create } from 'zustand';

interface AppState {
  mainCurrency: string;
  setMainCurrency: (currency: string) => void;
}

export const useAppStore = create<AppState>((set) => ({
  mainCurrency: 'USD',
  setMainCurrency: (currency) => set({ mainCurrency: currency }),
}));