fix: Double-charged shipping fee in Yoco payment + ops staff access

1. Fix Yoco payment amount calculation: order->total already includes
   shipping_fee, so don't add it again. Was charging 2x shipping.

2. Add authorization gate for ops staff access: users with is_admin=true
   can now access the ops page by scanning QR codes.

app/Providers/AppServiceProvider.php

@@ -30,5 +30,11 @@ class AppServiceProvider extends ServiceProvider
             $cartCount = session('cart') ? count(session('cart')) : 0;
             $view->with('cartCount', $cartCount);
         });
+
+        // Authorization gates
+        \Illuminate\Support\Facades\Gate::define('access-ops', function ($user) {
+            // Allow admin users to access ops
+            return $user->is_admin === true;
+        });
     }
 }