Because the Entity Framework model and context are in a netstandard classlib project the startup project needs to be specified.
cd ./src/BikeDataProject.Statistics/
dotnet ef migrations add InitialDb --startup-project ../BikeDataProject.Statistics.Service/BikeDataProject.Statistics.Service.csproj
cd ./src/BikeDataProject.Statistics/
dotnet ef database update --startup-project ../BikeDataProject.Statistics.Service/BikeDataProject.Statistics.Service.csproj