Function import_secrets 

pub fn import_secrets(
    vault: &mut Vault,
    murk: &mut Murk,
    pairs: &[(String, Zeroizing<String>)],
) -> Vec<String>

Import multiple secrets at once.

For each (key, value) pair, inserts the value into murk and ensures a schema entry exists. Returns the list of imported key names.

Values arrive already wrapped in Zeroizing so callers do not have to hold plaintext in a bare String across the import boundary.