Cleanup: Rename setup-runner-pyenv.sh and remove stale conda/pyenv from VMs

[mrveiss]

Problem

After #1898 (Python standardization to deadsnakes PPA):

1. Misleading filename: `autobot-infrastructure/shared/scripts/setup-runner-pyenv.sh` — content is now deadsnakes PPA install, but filename still says "pyenv". Should be renamed to `setup-runner-python.sh` (check for references first).

2. Stale installations on VMs: After deploying updated Ansible playbooks, old Python installations remain on disk:

   • .20: conda at `/home/autobot/miniconda3/` (~2-5 GB)
   • .20: pyenv at `/home/autobot/.pyenv/` (~500 MB)
   • Old bashrc entries for pyenv PATH/init

   These are inert (systemd now uses venv PATH) but waste disk space and could cause confusion.

Proposed Fix

1. Rename script file + update any references
2. Add Ansible cleanup tasks (optional, after verifying new venv works):
   • Remove `~/.pyenv/` directory
   • Remove conda installation
   • Clean up bashrc pyenv/conda blocks

Impact

Low — cosmetic/disk cleanup only, no functional impact.

Discovered During

#1898 (Python standardization)

[mrveiss]

Merged in PR #1931. Renamed setup-runner-pyenv.sh to setup-runner-python.sh, added cleanup-legacy-python.sh.