Add a Select All checkbox, to enable or disable all categories in the job filters

Add a select all checkbox in the job filters to automatically select or deselect all job categories in the job listings view filters.

Requested by 4377268-zen

Start by locating the job listings view filters and the existing category checkboxes. Trace how category selection is handled, then add the requested select-all behavior so one checkbox selects or deselects every job category. Done means the control stays consistent with the category selections in both directions.

Written by the indexing model from the issue text.