factor out repetition

[jhheider]

more DRY

[Copilot]

Pull Request Overview

This PR refactors repeated keypair-loading logic into a single helper and updates various commands to use it, making the code more DRY.

• Introduces get_keypair to centralize config loading and KeyData instantiation
• Updates print_public_key, get_fingerprint, verify_commit, and sign_from_hex to call get_keypair
• Removes duplicated config/keychain/secret-handling code from multiple functions

Comments suppressed due to low confidence (2)

bpb/src/main.rs:108

• Add a doc comment above get_keypair to explain its purpose (loading config, retrieving the secret, and constructing a KeyData).

fn get_keypair() -> Result<KeyData, Error> {

bpb/src/main.rs:108

• Consider adding unit tests for get_keypair to cover both successful key loading and error scenarios (e.g., missing keychain item or invalid hex).

fn get_keypair() -> Result<KeyData, Error> {