The vacation rental company Airbnb forecast third-quarter revenue below Wall Street estimates on Tuesday and reported a lower second-quarter profit, as it flagged weakening demand from US customers.Shares of the company were down about 12% after the bell.Domestic travel in the United States has been pressured since the start of the year as more Americans grow cautious about travel spending amid growing economic uncertainty.The San Francisco-based company reported quarterly profit of $555m compared to $650m ...