Add comprehensive skeleton screen implementation for sidebar to improve loading UX, matching the existing headerbar skeleton pattern. ## Features Added - **Sidebar skeleton screens**: Complete 1:1 recreation of sidebar structure during loading - **Responsive skeleton layouts**: Different layouts for expanded (164×30px) and collapsed (44×44px) states - **Skeleton component enhancements**: Extended SkeletonWrapper with new skeleton types (sidebar, button, sidebarNavItem, sidebarGroupTitle) - **Minimum loading time**: Integrated useMinimumLoadingTime hook with 500ms duration for smooth UX ## Layout Specifications - **Expanded nav items**: 164×30px with 8px horizontal margins and 3px vertical margins - **Collapsed nav items**: 44×44px with 4px bottom margin and 8px horizontal margins - **Collapse button**: 156×24px (expanded) / 36×24px (collapsed) with rounded corners - **Container padding**: 12px top padding, 8px horizontal margins - **Group labels**: 4px 15px 8px padding matching real sidebar-group-label styles ## Code Improvements - **Refactored skeleton rendering**: Eliminated code duplication using reusable components (NavRow, CollapsedRow) - **Configuration-driven sections**: Sections defined as config objects with title widths and item widths - **Fixed width calculations**: Removed random width generation, using precise fixed widths per menu item - **Proper CSS class alignment**: Uses real sidebar CSS classes (sidebar-section, sidebar-group-label, sidebar-divider) ## UI/UX Enhancements - **Bottom-aligned collapse button**: Fixed positioning using margin-top: auto to stay at viewport bottom - **Accurate spacing**: Matches real sidebar margins, padding, and spacing exactly - **Skeleton stability**: Fixed width values prevent layout shifts during loading - **Clean file structure**: Removed redundant HeaderBar.js export file ## Technical Details - Extended SkeletonWrapper component with sidebar-specific skeleton types - Integrated skeleton loading state management in SiderBar component - Added support for collapsed state awareness in skeleton rendering - Implemented precise dimension matching for pixel-perfect loading states Closes: Sidebar skeleton loading implementation
