MOSCOW — For President Vladimir Putin, the World Cup marks a moment of pride, a long-sought opportunity to showcase Russia’s achievements and bolster its international prestige. The Russian leader has made security of the tournament the top priority, ordering an array of measures to fend off any potential threats from the ground, sea or air. “This whole event was intended to be a soft power exercise for Russia,” said Mark Galeotti, a senior fellow at the Institute for International Relations in Prague who has closely followed Russian security agencies.