Remove all obsolete authentication, settings, admin, and demo-related components and pages

- Eliminated redundant components, pages, and layouts related to authentication (`login`, `register`, `password-reset`, etc.), user settings, admin, and demos.
- Simplified the frontend structure by removing unused dynamic imports, forms, and test code.
- Refactored configurations and metadata imports to exclude references to removed features.
- Streamlined the project for future development and improved maintainability by discarding legacy and unused code.

frontend/src/app/[locale]/dev/layout.tsx

@@ -0,0 +1,10 @@
+/**
+ * Dev Layout
+ * Shared layout for all development routes
+ */
+
+import { DevLayout } from '@/components/dev/DevLayout';
+
+export default function Layout({ children }: { children: React.ReactNode }) {
+  return <DevLayout>{children}</DevLayout>;
+}