- Refactor ActivityLogTimelineTableAction for better null handling and strict typing
- Update ActivitiesRelationManager to include causer activities
- Modernize timeline.blade.php:
  - Replace all Tailwind classes with custom CSS
  - Use x-heroicon components for better alignment
  - Implement full localization for empty states and changes
- Refactor filament-activity-log.css:
  - Remove comments and organize structure
  - Implement dynamic theme colors using Filament CSS variables
- Add missing localization keys (old, new, empty_state) to all languages