feat: add app header, sidebar, and mobile navigation components

- Implemented AppHeader component with theme toggle and connection status.
- Created AppSidebar component for navigation with connection status indicator.
- Added MobileNav component for mobile navigation with responsive design.
- Introduced shared components: DetailStat, EmptyState, ErrorState, LoadingSkeleton, and StatCard for consistent UI.
- Developed hooks for async data fetching: useAsync, useConfig, useDashboard, useGuilds, useMedia, useMessages, useRecordings, and useVoice.
- Added chatbot API functions for sending messages and managing chat history.

services/frontend/src/components/shared/index.ts

@@ -0,0 +1,5 @@
+export { DetailStat } from "./detail-stat";
+export { EmptyState } from "./empty-state";
+export { ErrorState } from "./error-state";
+export { LoadingSkeleton } from "./loading-skeleton";
+export { StatCard } from "./stat-card";