Build admin interface for content management

[Revmagi]

Create comprehensive admin dashboard for managing custom nodes and models.

Tasks

• Create admin dashboard layout
• Implement custom node management interface
• Add model management interface
• Build user management system
• Create data tables with filtering/sorting
• Add bulk operations support

Acceptance Criteria

• Admin can manage all content types
• Data tables are responsive and performant
• Bulk operations work correctly
• UI follows design system