Add comprehensive tests for authentication, settings, and password reset pages

- Introduced smoke tests for Login, Register, Password Reset, Password Reset Confirm, and Settings pages.
- Enhanced test coverage for all dynamic imports using mocks and added Jest exclusions for non-testable Next.js files.
- Added component-specific test files for better structure and maintainability.
- Improved test isolation by mocking navigation, providers, and rendering contexts.

frontend/src/app/(auth)/register/page.tsx

@@ -4,6 +4,7 @@ import dynamic from 'next/dynamic';
 
 // Code-split RegisterForm (313 lines)
 const RegisterForm = dynamic(
+  /* istanbul ignore next - Next.js dynamic import, tested via component */
   () => import('@/components/auth/RegisterForm').then((mod) => ({ default: mod.RegisterForm })),
   {
     loading: () => (