#77 UI: Admin Panel Layout and Navigation

Create main Admin Panel layout with navigation sidebar. Component: api/ui/templates/components/admin_panel/ Files: - admin_panel.html (Mako template) - admin_panel.css - admin_panel.js Features: - Left sidebar navigation with icons - Navigation items: Users, Roles, Tokens, API Keys, Invitations, Sessions, Audit Logs, Settings - Active state indication - Collapsible on mobile - Breadcrumb navigation - User role-based menu visibility - URL fragment routing (#/admin/users, #/admin/roles, etc.) - Smooth transitions between sections - Loading states for section changes Layout: - Header with tenant name and current user - Main content area for sub-components - Responsive design (1440x900 primary) With ultra attention to details and correctness. Before closing: write comment summarizing implementation with screenshot.