Move project to repository root

[constripacity]

Summary

• move the entire project file tree from the nested teacher-safe-scanner/ folder to the repository root so the default branch now exposes all documentation and source files at the top level
• ensure existing documentation, configuration, and source files remain unchanged aside from their new locations, making the changes visible without needing to drill into a subdirectory

Testing

• ruff check .
• mypy .
• pytest -q

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Codex Task