Add full-stack Pine Script export: backtest strategies can now be
converted to TradingView Pine Script v6 via natural language, CLI,
API, or the web UI.
- New `pine-script` skill with Python-to-Pine mapping table and v6 syntax guide
- CLI: `/pine <run_id>` slash command and `--pine` flag
- API: `GET /runs/{run_id}/pine` endpoint
- Frontend: Pine Script button on RunCompleteCard + modal code viewer with copy
- README: updated news, capabilities, skill count (65), CLI/API docs
warren618