Introduces XLSX export functionality to the user grades report.
Adds a checkbox for selecting XLSX export in the form interface.
Uses PhpSpreadsheet to generate and download detailed Excel
files containing user grades and quiz attempts.
Enhancement enables convenient data export for offline analysis
and sharing.
Extracts and refactors user selection logic by moving user selector
and form functionality into separate class files. This enhances code
modularity and reusability across different parts of the application.
Adds a detailed user grades report page that displays quiz attempts
and grades for selected users, improving user grade reporting.
Updates admin settings to include detailed report page link for
navigation ease.
