Backend improvements:
- Add document_count annotation to FolderViewSet queryset
- Add document_count field to FolderSerializer
Frontend improvements:
- Add folder_path display in document cards with folder icon
- Add document count badges in folder tree
- Add breadcrumbs navigation showing current folder path
- Improve folder selector button to show selected folder name
- Add clear filter button (X) to folder selector
- Add highlighted style for selected folder in selector
- Update Document interface to include folder and folder_path fields
UI enhancements:
- Folder path shown in sky-blue color with FolderOpen icon in cards
- Document count displayed in gray badge next to folder names
- Breadcrumbs allow quick navigation back to root
- Selected folder highlighted with sky-blue background
- Visual feedback for folder selection state