feat(lesson-preparation): add readonly view, anchor node selector, and type guards
- Add lesson-plan-readonly-view for viewing published plans
- Add anchor-node-selector and textbook-segments for canvas anchor positioning
- Add i18n-errors and type-guards lib utilities
- Add lesson-plan-provider-setup for provider initialization
- Update actions, data-access (knowledge, versions, main), publish-service
- Update blocks (blackboard, exercise, homework, import, key-point, objective, reflection)
- Update editor, node-editor, node-edit-panel, pickers, and providers