- Add ThemePreference type and useTheme hook for theme state management
- Create CSS theme architecture with 8 built-in color themes
- Build ThemeSelector component with live preview and keyboard navigation
- Add theme toggle to Header with quick-switch capability
- Integrate Appearance section into SettingsModal
- Wire theme system into App component with system preference detection
- Add comprehensive tests for useTheme, ThemeSelector, and Header
- Include theming documentation in dashboard README
- Add changeset for patch release
- Add section expansion state management with localStorage persistence
- Update section headers with chevron toggle controls
- Implement conditional task row rendering based on section state
- Add Expand All / Collapse All toolbar controls
- Add CSS styles for chevron rotation animation and section headers
- Add comprehensive tests for collapsible section behavior
