Mutations with React Query

TODO i18n: Full body translation pending. Title and description are localized; the body below remains in Portuguese for now.

useMutation cobre POST/PUT/DELETE. No sucesso, invalide queries relacionadas para refetch.

const mutation = useMutation({
  mutationFn: async (title: string) => {
    /* POST ... */
    return { id: Date.now(), title };
  },
  onSuccess: () => {
    queryClient.invalidateQueries({ queryKey: ['todos'] });
  },
});