Danbury’s Zoning Board of Appeals has approved a variance allowing 75 additional parking spaces at 36 Apple Ridge Road, where a vacant high-tech warehouse is being converted into industrial condos. The property borders the city’s new west side high school, opening next month, which complicated zoning. City officials acknowledged the conflict was partly caused by their own rezoning for the school. Developers say the added parking is critical to attracting tenants. The variance brings the total parking count to 329 spaces on the 11-acre site.