Necessary for smoia#154

This pull request adds informative logging throughout the phys2cvr workflow and refactors the lag map and regressor loading logic for clarity and robustness. The changes improve transparency of data loading steps, clarify the order of operations, and make lagged regression handling more explicit.

Logging improvements:

• Added logging statements for loading functional data, mask, ROI, physiological data, and lag map to increase transparency during workflow execution. [1] [2] [3] [4] [5]

Lag map and regression handling refactor:

• Moved lag map loading and information extraction earlier in the workflow, and improved delta lag calculation with additional checks for numerical tolerance.
• Refactored lagged regression logic to separate handling of lag map and max lag scenarios, with clearer logging and step calculation. [1] [2]

Robustness improvements:

• Improved error handling and warnings when loading regressors, ensuring fallback to estimation when files are missing.
• Added checks for shape compatibility between mask/ROI/lag map and functional data to prevent downstream errors. [1] [2] [3]

Performance and clarity:

• Updated loop variable names and logging in lagged regression to clarify progress and improve readability.