Restructure layout components architecture

- Move layout components from layouts/ directory to components/layout/
- Reorganize divider component from data-display to layout category
- Add comprehensive layout component collection including aspect-ratio, bento-grid, box, breakpoint-container, center, column, dashboard-shell, feed-layout, flex, grid-container, hstack, list-detail-layout, scroll-container, section, sidebar-layout, stack, supporting-pane-layout, tabs-container, and vstack
- Update all demo components to match new layout structure
- Refactor routing and index exports to reflect reorganized component architecture

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

projects/demo-ui-essentials/src/app/demos/tree-view-demo/tree-view-demo.component.scss

@@ -1,4 +1,4 @@
-@use '../../../../../ui-design-system/src/styles/semantic/index' as *;
+@use '../../../../../ui-design-system/src/styles/semantic' as *;
 
 .demo-container {
   padding: $semantic-spacing-component-lg;