Documentation update for DBLab 4.0

Description

Update the documentation to reflect the changes introduced in DBLab 4.0:

  • Validate existing changes in the currently open merge request DBLab 4.0 docs (!681 - merged)
    • Ensure alignment with the final implementation
  • Add documentation for new functionality:
    • branches and snapshots: provide a how-to and reference guide in the same format as previous guides
    • If there are suggestions for improving structure or content — feel free to include them
  • Update the Cloning section:
    • Refresh UI screenshots and update the related UI description
  • Update the Tutorial section:
    • Integrate new features (branches, snapshots) into the flow
    • Ensure all steps are still relevant and accurate

Goal

Documentation must fully reflect the current product state and cover all features introduced in DBLab 4.0.