pub fn generate(count: usize) -> Vec<(String, String)>Expand description
Generates count one-time backup recovery codes.
Each code is formatted as xxxx-xxxx (8 lowercase alphanumeric characters
split by a hyphen). Returns a Vec of (plaintext_code, sha256_hex_hash)
tuples. Store only the hashes; display the plaintext codes to the user
once. Verify a submitted code with verify.
Uses rejection sampling over OsRng to avoid modulo bias.
Requires feature "auth".