Trying to install bidet but stuck on first step - valve won't turn

No matter what I can't turn my toilet water valve. It moves maybe a milimeter both directions. Have been trying to wiggle it manually, no luck. Used tools, nothing. Just recently moved into this apartment, other bathroom can turn no problem. It looks like heavy calcification, there's literally white coating. Tried hot water multiple times and WD-40 twice with no luck. Any other way around this without having a plumber involved?