Function generate_code_phrase 

pub fn generate_code_phrase() -> String

Generate a fresh code phrase like 73-2QXC4P (~36 bits entropy).

Format: NN-XXXXXX where NN is two random decimal digits and XXXXXX is six random RFC-4648 base32 characters. ~6.6 + 30 = ~36.6 bits entropy. Easy to read aloud; trivially copied by ear.