Hidrock Properties is planning a new 161-room hotel on a Midtown assemblage it acquired for $47 million, according to property records filed with the city Friday. Financial District-based Hidrock filed plans for a 116,000-square-foot, 31-story hotel at 12 East 48th Street. The family-led development firm, led by CEO Abraham Hidary, acquired the three sites necessary to build the project in 2014, beating out several competitors and drawing up initial plans to build a condominium building.