make ssh also work for modal

[wenting-zhao]

• add an additional step to set up a git user
  • uv run commit0 setup-git-user simpy this should be executed after the build step
• clean separation of steps that require and do not require sudo
  • all steps that require sudo permissions are moved to the setup-git-user step
  • during test steps, no more key writing, thus no need for sudo after the setup-git-user step