By Jake Cordell and Essi Lehto TBILISI/VAALIMAA, Finland (Reuters) -Some Russian men headed swiftly to the borders on Thursday after President Vladimir Putin ordered a partial mobilisation, with traffic at frontier crossings with Finland and Georgia surging and prices for air tickets from Moscow rocketing. Putin on Wednesday ordered Russia’s first mobilisation since World War Two and backed a plan to annex swathes of Ukraine, warning the West he was not bluffing when he said he’d be ready to use nuclear weapons to defend Russia. Prices for air tickets out of Moscow soared above $5,000 for one-…