Refactor of group 4 (reporting and visualization) completed.

- Remove unused imports from reporting modules

- Replace bare except: clauses with except Exception as e and add warning logs

- Convert silent YAML reload failure in pdf_report.py into logged fallback behavior

- Replace stray print() logging in ttv_plots.py with module logger

- Optimize confidence band computation by reducing redundant np.percentile() calls

- Smoke-test reporting changes via generate_report() and direct periodogram plotting

- Introduce ModelComponentsConfig dataclass to simplify compute_model_components signature and update all call sites.

- Optimize compute_grid_bands by vectorizing np.percentile calls to reduce sorting overhead.

- Establish testing foundation for the reporting package, including synthetic fixtures, unit tests for core computation functions, and a smoke test for the PDF report generation pipeline.