By James Mackenzie, Natalia Zinets and Oleksandr Kozhukhar KYIV/LVIV, Ukraine (Reuters) – Rescue workers on Thursday dug survivors out of the rubble of a theatre in the besieged city of Mariupol which Ukraine said had been hit by a Russian air strike as people sheltered there from bombardments. Russia denied striking the theatre. But Ukraine’s capital Kyiv came under renewed Russian shelling on Thursday as the war entered its fourth week. Western sources and Ukrainian officials said Russia’s assault had stalled. Officials from both sides meanwhile met again for peace talks, but they said their…