- Add Theme struct with 3 predefined themes (dark/light/druntime)
- Add Profile struct for named configuration profiles
- Add ErrorBanner with severity levels and auto-dismiss
- Add unit tests for theme, error banner, and models
- Update CHANGELOG.md and PROJECT_STATE.md
- Update Makefile with test-coverage and verify targets
- Add build.sh script for cross-platform builds with SHA256 checksums
- Implement integration tests for full workflow (add/list/get/update/export/delete)
- Add config integration test
- Update project state documentation
- Add export command with JSON file output and size summary
- Add import command with replace/merge strategies and dry-run preview
- Add integration test for export/import round-trip via storage layer
- Update project state documentation