S he had long refused to join social media, preferring to eschew the machinery of celebrity. So if Sandra Bullock’s arrival on Instagram last week says anything, it’s that the Oscar-winning actor – once routinely dubbed “America’s sweetheart” – is ready to embrace the spotlight again. After years of near-total retreat from public life, Bullock is suddenly everywhere: making her first major convention appearance in years at CinemaCon, teasing Practical Magic 2 alongside Nicole Kidman, and using her first Instagram post to revive one of the most beloved moments of her career – the “midnight margaritas” scene from the original 1998 film. Kidman quickly welcomed her to the platform in the comments, turning Bullock’s debut into a miniature Practical Magic reunion before the sequel’s press campaign had properly begun. At CinemaCon, the pair slipped easily back into the chemistry that made the film an enduring cult favourite.…