feat: add admin UI components and enhance client identity management

- Implement AdminSidebar for navigation in the admin panel.
- Create AdminPageShell for consistent layout across admin pages.
- Add AdminAgentsPage to list all configured agents.
- Add AdminNetworksPage to display all agent networks.
- Add AdminWorkflowsPage to show configured workflows.
- Add AdminHomePage for an overview of agents, networks, and workflows.
- Add AdminSettingsPage for client-side preferences and session controls.
- Add AdminToolsPage for tool discovery and observability.
- Introduce registry functions to list agents, networks, and workflows.
- Implement client identity management with getClientIdentity and local storage handling.
- Enhance Reasoning component with autoClose prop for better user experience.