- Add POST /api/knowledge/import endpoint for .md and .zip files
- Add GET /api/knowledge/export endpoint with markdown/json formats
- Import parses frontmatter (title, tags, status, visibility)
- Export includes frontmatter in markdown format
- Add ImportExportActions component with drag-and-drop UI
- Add import progress dialog with success/error summary
- Add export dropdown with format selection
- Include comprehensive test suite
- Support bulk import with detailed error reporting
