- Updated `RootLayout` to include user authentication logic and loading states.
- Removed redundant user authentication logic from `Page` component.
- Enhanced `AppSidebar` to fetch and display logged-in user information.
- Replaced `GravatarAvatar` with new `Avatar` component for user profile images.
- Added new pages for comment, file, post, and user management.
- Introduced utility functions for generating Gravatar URLs and fallback avatars based on usernames.
- Cleaned up unused imports and components across various files.
