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/user-layouts/sell_design.blade.php

@@ -133,7 +133,7 @@
                                             <label>Item URL</label>
                                             <input type="text" class="form-control" id="product_url" name="itemUrl" placeholder="Item URL">
                                             <!-- <div class="input-group">
-                                                <span class="input-group-addon" id="basic-addon3">{{ url() . "/teamstore/" . $store_array[0]->StoreUrl . '/'}}</span>
+                                                <span class="input-group-addon" id="basic-addon3">{{ url('/') . "/teamstore/" . $store_array[0]->StoreUrl . '/'}}</span>
                                                 <input type="text" class="form-control" id="product_url" name="itemUrl" aria-describedby="basic-addon3" data-error="#err-itemUrl" >
                                             </div>
                                             <span id="err-itemUrl"></span>  -->