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

app/Models/teamstore/TeamStoreModel.php

@@ -53,7 +53,7 @@ class TeamStoreModel extends Model {
 		$i = DB::table('cart_tmp')
 						->where('CartKey', $cartKey)
 						->groupby('CartKey')
-						->get();
+						->first();
         return $i;
 	}