Ukrainian drones hit an oil terminal and a naval base in St Petersburg just hours before President Vladimir Putin was due to open his flagship economic forum, in a strike aimed at puncturing the Kremlin’s image and underscoring the exposure of Russia’s major cities. The assault on St Petersburg, Mr Putin’s home city and host of his own glitzy version of ‘Davos’ — an annual showcase meant to lure foreign investors — came as both sides intensified attacks in a war now more than four years old, with no clear end in sight.…