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/scss/_variables.scss

@@ -13,7 +13,7 @@
 $base-typography-font-family-sans: 'Inter', ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, 'Noto Sans', sans-serif;
 $base-typography-font-family-display: 'Inter', ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, 'Noto Sans', sans-serif;
 
-@import '../../../shared-ui/src/styles/semantic';
+@import '../../../ui-design-system/src/styles/semantic';
 
 // These overrides will cascade through all semantic typography tokens
 // that use $base-typography-font-family-sans and $base-typography-font-family-display