The 49ers are technically alive. And, hey, they’re in the playoffs. That’s good, right? Right? So why do they seem so glum? Yes, the 49ers are down bad, and now they need to channel that negative energy into a win on Sunday in the NFC Wild Card Round against the Eagles. It’s hard to blame the Niners for the negative vibes: They’re coming off a Week 18 loss to the Seahawks —a game San Francisco treated like a playoff game and were subsequently stomped in. The Niners emptied the tank, but drove in reverse. It felt like the season was on the line, alongside the No. 1 seed and NFC West crown last Saturday. It makes the playoffs feel like a loser’s bracket. But so it...