feat(lesson-preparation): major update with AI features, schedules, and new components
- Add actions-schedules.ts and data-access-schedules.ts for schedule management
- Add AI differentiation, AI feedback, consistency check dialogs
- Add attachment-picker, curriculum-heatmap, print-view, version-diff-view
- Add lesson-plan-mobile-view and schedule-dialog components
- Add lib: ai-differentiation, ai-feedback, auto-layout, consistency-check,
curriculum-coverage, export, version-diff
- Add history-slice hook for version history
- Update existing components, hooks, providers, services, types
- Add teacher lesson-plans heatmap and library pages
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