Add tests and coverage report, update modules

[aeiwz]

This pull request introduces several improvements and bug fixes across the codebase, focusing on enhanced logging, improved error handling, and minor API and UI adjustments. The most significant change is the refactoring of metbit/nmr_preprocess.py to replace print-based debugging with structured logging, making the codebase cleaner and more maintainable. Additional changes improve error handling and user feedback, and update UI components for better accessibility and consistency.

Logging and Debugging Improvements:

• Replaced all print statements with Python's logging module for debug, info, and error messages in metbit/nmr_preprocess.py, providing more structured and configurable logging throughout the NMR preprocessing pipeline. [1] [2] [3] [4] [5] [6] [7] [8]

Error Handling and API Robustness:

• Improved error raising in metbit/peak_processe.py by raising a ValueError instead of printing and raising, ensuring proper exception handling.
• Added validation to plotting methods in metbit/plotting.py to require file_name when save_plot=True, raising a ValueError if not provided. Also fixed the type annotation for the file_name parameter in splot. [1] [2] [3] [4]
• Added a check in metbit/pretreatment.py to raise a ValueError for unknown scaler types, improving input validation.
• Fixed logic in metbit/pls.py to handle n_comp=None by setting it to the minimum of sample and feature count, and corrected component indexing in predict. [1] [2]

UI and Accessibility Enhancements:

• Updated the ThemeToggle component in docs/app/components/ThemeToggle.tsx to explicitly set type="button" on all buttons, improving accessibility and preventing unintended form submissions. [1] [2] [3]
• Replaced anchor tags with Next.js Link components in docs/app/page.tsx for navigation, ensuring proper client-side routing and accessibility.

Minor Refactors and Cleanups:

• Removed unnecessary return print(...) statements in several methods, replacing them with just print(...) for clarity and correctness in metbit/genpage.py, metbit/lazy_opls_da.py, and metbit/metbit.py. [1] [2] [3] [4] [5]

These changes collectively improve the maintainability, reliability, and usability of the codebase.Add a comprehensive test suite and coverage output (coverage.json); update pytest.ini and include many new test files under tests/. Update docs components (docs/app/components/ThemeToggle.tsx and docs/app/page.tsx). Modify multiple metbit modules and include regenerated pycache (.pyc) artifacts. Update .gitignore to ignore metbit/pycache.