BEREZNIKI, Russia — Dmitry Rybolovlev, the Russian fertilizer tycoon who in February bought the most expensive apartment ever sold in New York City — the $88 million penthouse at 15 Central Park West — may have done a lot for real estate values there. But here in this old mining city in the Ural Mountains, where he made his fortune, not just property values, but properties too, have been plunging…
