ANTON ZVEREV and ANDREW OSBORN A Russian judge has remanded Kremlin critic Alexei Navalny in pre-trial detention for 30 days for violating the terms of a suspended jail sentence, ignoring calls from Western countries to free the opposition politician immediately. The ruling, a day after police detained him at the airport as he returned home for the first time since being poisoned by a military-grade nerve agent, may be the prelude to him being jailed for years. Moscow's prison service has applied to convert a suspended 3.5 year embezzlement sentence in the same case, which he says was trumped up,…