Two annual spring traditions - the Greater Concord Chamber of Commerce's spring ART CONCORD and the annual exhibit of the Friends Program's art auction items - are joining forces for a large-scale, one-night collaborative art event highlighting the talent and artistry of Concord-area artists on April 28 from 4:30 to 6:30 p.m. at participating galleries.All of the galleries welcome you for current Art Concord exhibits, and many of the following venues will showcase this year's custom-designed Adirondack chairs that will be auctioned at the Friends' 12th annual charity auction on May 20. Auction…