Refactor console layout and sidebar components; implement user authentication and loading states

- 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.

web/src/utils/common/username.ts

@@ -0,0 +1,22 @@
+import { User } from "@/models/user";
+
+export function getFallbackAvatarFromUsername(username: string): string {
+  if (!username) {
+    return "N";
+  }
+  const firstChar = username.charAt(0);
+  if (/[a-zA-Z]/.test(firstChar)) {
+    return firstChar.toUpperCase();
+  }
+  return firstChar;
+}
+
+export function getFirstCharFromUser(user: User): string {
+  if (user.nickname) {
+    return getFallbackAvatarFromUsername(user.nickname);
+  }
+  if (user.username) {
+    return getFallbackAvatarFromUsername(user.username);
+  }
+  return "N";
+}