Internet activists declared victory over the nation’s big cable companies Thursday after the Federal Communications Commission voted to impose the toughest rules yet on broadband providers like Comcast, Verizon and AT&T to prevent them from creating paid fast lanes and slowing or blocking web traffic. But Georgia Republicans said the new rules would obstruct innovation and expansion of Internet connectivity, particularly in rural parts of the state. The 3-2 party-line vote, with Democrats in the majority, ushered in a new era of government oversight for an industry that has had relatively little.