Rename project from Beatstep to Samplestep and update related configurations

Commit notes

- Updated all instances of "Beatstep" to "Samplestep" across the codebase, including environment variables, API endpoints, and documentation. - Modified Docker configurations to reflect the new project name and user credentials. - Adjusted frontend components and metadata to align with the new branding. - Ensured all references in the backend and frontend are consistent with the new project identity.