Cleanup: remove orphaned duplicate code, add .gitignore

  - Removed 102 lines of orphaned duplicate PosixComputerController class
  - Fixed code structure: PosixComputerController defined only once (lines 198-267)
  - Reduced file size from 658 to 556 lines

  - Added .gitignore for Python/Windows artifacts:
    * __pycache__/ and *.pyc
    * venv/, build/, dist/
    * *.bak, *.backup
    * windows/build/, windows/Output/
    * IDE files (.vscode, .idea)

  - Removed __pycache__ from git staging (no longer tracked)

Documentation already present in README.md and windows/README.md.