For more than a decade, Denver city officials have winced as they’ve watched puffs of marijuana smoke rise above Civic Center park during 4/20 gatherings at the symbolically important time of 4:20 p.m. After the legalization of recreational marijuana took effect in Colorado four years ago, those grimaces spread — finding a quiet echo among many on the business side who feared that such open flouting of the continuing ban on public consumption could harm the wider public acceptance of the fledgling industry. This year, the industry has taken control of the event for the first time, after Euflora, a growing chain of dispensaries that started on the 16th Street Mall, won the right to step in for longtime permit-holder Miguel Lopez, a sometimes-combative pro-marijuana activist.