PHILADELPHIA — Philadelphia Mayor Jim Kenney on Tuesday signed an executive order banning the possession of firearms and other deadly weapons at city recreation centers and playgrounds, a move that could reignite a long-standing debate about whether the city should be able to write its own gun laws. The action came weeks after Tiffany Fletcher was fatally struck by a stray bullet from a nearby shooting while working at the Mill Creek rec center. Kenney, speaking at a news conference after signing the order, choked up while describing how Parks and Recreation employees on Monday lined the stree…