KATHMANDU, Nepal — Polls opened across Nepal on Thursday in the first nationwide election since last year’s violent, youth-led uprising forced the government from power. Security forces patrolled streets and guarded polling stations across the Himalayan nation of about 30 million people as voters lined up to cast their ballots. Counting of votes will begin later Thursday, with results expected over the weekend. Authorities banned vehicles from the streets and prohibited political rallies and public gatherings. All forms of campaigning are barred on election day. Nearly 19 million people are eligible to vote, according to the Election Commission. Voters are directly electing 165 members to the House of Representatives, the lower chamber of Parliament. The remaining 110 seats in the 275-member body will be allocated through a proportional representation system, under which political parties nominate lawmakers based on their share of the vote. The election is widely seen as a three-way contest, shaped by voter frustration over widespread corruption and demands for greater government acco