Add node group management interface with automatic user assignment and traffic-based grouping.
Features:
- Node group CRUD with traffic range configuration
- Three grouping modes: average, subscription-based, and traffic-based
- Group recalculation with preview and history tracking
- Subscribe-to-group mapping management
- User subscription group locking
- Group calculation history with detailed reports
- Multi-language support (en-US, zh-CN)
- Enhanced node and subscription forms with group selection
