Implements user login and registration

Replaces the demo login page with a dedicated login and registration component.
This allows users to create accounts and log in, enabling authentication features.

Simplify Login, remove registration for now

Adds a login page with username and password fields.
Includes input validation, loading state, error handling,
and a success message after successful login.
Registration has been temporarily disabled.

src/app.ts

@@ -60,7 +60,7 @@ export async function createAppInstance() {
       {
         path: '/login',
         name: 'login',
-        component: () => import('./pages/LoginDemo.vue'),
+        component: () => import('./pages/Login.vue'),
         meta: { requiresAuth: false }
       },
       // Pre-register module routes