Students braved long lines and technology snafus in the name of breakfast at the chaotic opening of Belmont’s new Einstein Bros. Bagels. Chosen based on student requests for healthier food options — and bagels specifically — Bruins can now treat themselves to a full coffee bar and all-day breakfast at the university’s new eatery, which opened its doors Thursday. And on-campus customers welcomed Einstein Bros. by queuing up eagerly in a line that snaked throughout the lobby of