Fix Laravel 5.5 compatibility issues - view helpers, collections, and auth routes

- Replace {{ url() }} with {{ url('/') }} in all blade templates to fix object-to-string conversion errors
- Update TeamStoreModel::selectTeamStoreGroupByCartKey() to use first() instead of get() for Laravel 5.5 Collections
- Fix TeamStoreController to access object properties directly instead of using array syntax [0]
- Update authentication routes to use Laravel 5.5 method names (showLoginForm, login, logout)
- Update login/register links from /auth/login to /login throughout views (navbar, app, auth pages)
- Verify cart, login, and register pages working with HTTP 200 status

resources/views/layout/navbar.blade.php

@@ -50,10 +50,10 @@
                             </li>
                         @else
                             <li>
-                                <a href="{{ url('/auth/login') }}" title="Login">Sign in</a>
+                                <a href="{{ url('/login') }}" title="Login">Sign in</a>
                             </li>
                             <li>
-                                <a href="{{ url('/auth/register') }}" title="Register">Register</a>
+                                <a href="{{ url('/register') }}" title="Register">Register</a>
                             </li>
                         @endif