phsl / new-api

- Add new PrefillGroup model with CRUD operations
  * Support for model, tag, and endpoint group types
  * JSON storage for group items with GORM datatypes
  * Automatic database migration support

- Implement backend API endpoints
  * GET /api/prefill_group - List groups by type with admin auth
  * POST /api/prefill_group - Create new groups
  * PUT /api/prefill_group - Update existing groups
  * DELETE /api/prefill_group/:id - Delete groups

- Add comprehensive frontend management interface
  * PrefillGroupManagement component for group listing
  * EditPrefillGroupModal for group creation/editing
  * Integration with EditModelModal for auto-filling
  * Responsive design with CardTable and SideSheet

- Enhance model editing workflow
  * Tag group selection with auto-fill functionality
  * Endpoint group selection with auto-fill functionality
  * Seamless integration with existing model forms

- Create reusable UI components
  * Extract common rendering utilities to models/ui/
  * Shared renderLimitedItems and renderDescription functions
  * Consistent styling across all model-related components

- Improve user experience
  * Empty state illustrations matching existing patterns
  * Fixed column positioning for operation buttons
  * Item content display with +x indicators for overflow
  * Tooltip support for long descriptions