Photo: Gareth Cattermole/Getty Images “This is the biggest weekend of our lives,” Robbie Miller, an affable 32-year-old Scotsman, tells me in between gulps of lager. His friend Jordan Colligan concurs: “I don’t think people realize how big this actually is.” On this blustery, sun-dappled afternoon, the two friends are seated outside the Blue Bell pub in Cardiff, Wales, where they’ve been pregaming since 10 a.m. Eventually they’ll stroll down to Principality Stadium, joining the tens of