Release 2.1.1

What's Changed

This is a security patch release to fix a state handling bug with single-signer mode. This does not affect MPC/Cosigner mode.
Single signer mode is now unsupported, but the issue is patched and the functionality is still available. To run in single-signer mode, run horcrux signer start --accept-risk

• CLI tidy by @agouin in #132
• Fix single signer state load bug by @agouin in #131

Full Changelog: v2.1.0...v2.1.1