Replace shell-based keychain implementation with keybase/go-keychain library

- Replaced exec.Command calls to /usr/bin/security with native keybase/go-keychain API
- Added comprehensive test suite for keychain operations
- Fixed binary data storage in tests using hex encoding
- Updated macse tests to skip with explanation about ADE requirements
- All tests passing with CGO_ENABLED=1

go.mod

@@ -9,6 +9,7 @@ require (
 	github.com/btcsuite/btcd/btcec/v2 v2.1.3
 	github.com/btcsuite/btcd/btcutil v1.1.6
 	github.com/btcsuite/btcutil v0.0.0-20190425235716-9e5f4b9a998d
+	github.com/keybase/go-keychain v0.0.0-20230307172405-3e4884637dd1
 	github.com/oklog/ulid/v2 v2.1.1
 	github.com/spf13/afero v1.14.0
 	github.com/spf13/cobra v1.9.1