feat(gitstore): migrate to new client options API and disable commit signing

- Updated git operations to leverage `ClientOptions` for authentication and configuration, replacing the deprecated `AuthMethod`.
- Implemented logic to disable GPG commit signing in repositories to prevent signature errors in automated workflows.
- Upgraded dependencies in `go.mod` and `go.sum` to align with the latest `github.com/go-git/go-git/v6` alpha releases.
- Added unit tests to verify commit signing is properly disabled in repositories.

Closes: #4341