It’s been a long six months since the 49ers’ season ended in heartbreaking fashion in the NFC Championship Game. But football is back, and the Niners’ road to redemption begins with training camp, which starts this week in Santa Clara. This is a magical time of the season, training camp. It means everything. It means nothing. It’s weeks of practice and a handful of practice games and despite all of that football, it’s hard to deduce what anything actually is. But as we head into the abyss, there are a few rules to remember: The defense will have a head start on the offense. Or is it the other …