- Add html_report.py module for Playwright-based screenshot generation
- Add generate_html_report() method to SimpleRotationStrategy
- Modify backtest_viewer.html to use window-scoped variables for external injection
- Inject monthly/yearly returns table into screenshot
- Auto-generate HTML report in __main__ after export_results()
Output: simple_rotation_html_report.png with ranking table + monthly returns
- Record position_weights in daily_records during backtest run
- Export weight field per held asset in detail JSON
- Display weight percentage in backtest_viewer holdings cards
- Force-add backtest_viewer.html (previously ignored by *.html rule)
