Add pre-commit hooks and ruff code quality configuration
- Add .pre-commit-config.yaml with trailing whitespace, ruff linter/formatter
- Configure ruff in pyproject.toml with selected rules (E, F, W, I, UP, B, C4, SIM)
- Add F401 to unfixable to preserve re-exported imports in __init__.py files
- Fix BacktestMetrics import in backtesting/engine.py
- Update todos.md with enhanced trade discovery and database implementation tasks
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>