It’s a shocking side effect. Mayor Zohran Mamdani’s plan to hike city property taxes by 9.5% could be a double whammy for residents in the increasingly unaffordable Big Apple — as the plan could send electric and gas bills soaring. The democratic socialist mayor pitched hiking property taxes for the first time since the turn of the century to prop up his massive $127 billion budget proposal — but experts warn New York utilities Con Edison and National Grid would simply pass the extra costs on