Added a default fallback for DataTables language selection if lang_datatables_language is undefined. Refactored checkbox event handling in qslprint.js to ensure proper attachment after DataTable redraws, prevent duplicate handlers, and keep the 'select all' checkbox in sync. Also improved checks for AJAX response data in markSelectedQsos and removeSelectedQsos.
Added a 'qso-checkbox' class and value attribute to QSO checkboxes in the QSL print table for easier selection and identification. Updated JavaScript to use the new class for batch selection, row highlighting, and QSO actions, improving code clarity and maintainability.
Replaced all occurrences of the '.qslprint' class selector with the more specific '#qslprint_table' ID selector for table row and checkbox operations. This improves selector accuracy and ensures the correct table is targeted for QSL print actions.
