Britain is putting on a display of birthday pageantry Saturday for King Charles III, a military parade that will be the Princess of Wales ’ first public appearance since her cancer diagnosis early this year. The annual event is also a show of stability by the monarchy after months in which both the king and Kate, wife of heir to the throne Prince William, have been sidelined by cancer treatment. STAY IN THE KNOW Watch NBC10 Boston news for free, 24/7, wherever you are. Get Boston local news, weather forecasts, lifestyle and entertainment stories to your inbox. Sign up for...