PROVIDENCE, R.I. — Mayor Jorge O. Elorza unveiled a proposed $734.3 million 2017-18 city-school budget Wednesday, a plan that included $7 million of increased spending for schools and youth programs, more police officers and firefighters, a municipal identity card program and no tax rate increase.If approved as proposed, the budget would represent an approximately $20 million increase over this year’s spending, a jump of 2.2 percent.