Implement scalable prime generator

Write a function first_n_primes(n) that returns the first n prime numbers in ascending order. Constraints: - 1 ≤ n ≤ 100,000. - Aim for O(n log log n) expected time and near-linear memory. - Avoid repeated trial division per candidate; use an efficient sieve and a tight upper bound estimate for the nth prime. - Handle n=0 and n=1 edge cases cleanly. - Include unit tests for n ∈ {0,1,5,10,100,100000} and verify the last prime for n=100000 equals the known value. - Describe the complexity and key constants that dominate runtime for large n.