Implement frontend authentication system with login/registration

- Add comprehensive authentication module with mock service
- Create login and registration components with form validation
- Implement protected routing with yew-router
- Add responsive UI styling with gradient design
- Enable JWT token persistence via localStorage
- Support demo credentials (demo/password) and flexible auth for development

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/components/mod.rs

@@ -0,0 +1,5 @@
+pub mod login;
+pub mod register;
+
+pub use login::Login;
+pub use register::Register;