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/auth/register.blade.php

@@ -125,7 +125,7 @@
 							<div class="col-xs-12">
 								<hr />
 								<p class="text-center">Have already an account?</p>
-								<a href="{{ url('/auth/login') }}" type="submit" id="btn-login" class="btn btn-success btn-block">Login here</a>
+							<a href="{{ url('/login') }}" type="submit" id="btn-login" class="btn btn-success btn-block">Login here</a>
 							</div>
 						</div>
 					</div>