Renamed generic 'stats' variables to more specific names such as 'domainStats', 'errorStats', 'tldStats', and 'importStats' across controllers and views. This improves code readability and reduces ambiguity when handling different types of statistics in the application.
Introduces error log tracking with new ErrorLog model, controller, views, and migration. Adds admin UI for viewing, resolving, and deleting errors. Implements bulk actions for users and notification groups, refactors domain filtering/pagination, and centralizes admin access checks using Auth::requireAdmin().
