Document batch overview - #8

This pull request refactors and documents the batch_overview Shiny module, improving code clarity, maintainability, and user experience. The main changes include reorganizing imports, enhancing documentation, restructuring the calculation and display of batch metrics, and improving error handling and UI responsiveness.

Code organization and import handling:

• Reorganized imports, added detailed comments, and introduced _add_import_path to ensure the circStudio package is reliably imported, improving code clarity and maintainability.

Documentation and code clarity:

• Added comprehensive docstrings and inline comments throughout the module to explain the purpose, parameters, and return values of functions, as well as the logic behind key code blocks. [1] [2]
• Grouped code sections with clear headers to separate metric calculation, UI, and server logic. [1] [2]