**Description:** Tune hyperparameters for ARIMA, XGBoost, and LSTM using Optuna. **Acceptance Criteria:** - Save best params to `artifacts/best_params.json`. - Plot optimization history and save to `plots/optuna_history.png`. - Use meaningful search spaces.
Description:
Tune hyperparameters for ARIMA, XGBoost, and LSTM using Optuna.
Acceptance Criteria:
artifacts/best_params.json.plots/optuna_history.png.