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/Http/Middleware/TrimStrings.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace App\Http\Middleware;
+
+use Illuminate\Foundation\Http\Middleware\TrimStrings as Middleware;
+
+class TrimStrings extends Middleware
+{
+    /**
+     * The names of the attributes that should not be trimmed.
+     *
+     * @var array
+     */
+    protected $except = [
+        'password',
+        'password_confirmation',
+    ];
+}