Show HasRoles import in installation step 9

The installation page only showed the in-class `use HasRoles;` without
the import, so copying it literally produces a trait-not-found error.
Now matches the full pattern used on the other docs pages.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: freekmurze

docs/installation-laravel.md

@@ -48,11 +48,20 @@ See the "Prerequisites" documentation page for compatibility details.
 
         php artisan migrate
 
-9. **Add the necessary trait to your User model**: 
+9. **Add the necessary trait to your User model**:
 
-        // The User model requires this trait
+    ```php
+    use Illuminate\Foundation\Auth\User as Authenticatable;
+    use Spatie\Permission\Traits\HasRoles;
+
+    class User extends Authenticatable
+    {
         use HasRoles;
 
+        // ...
+    }
+    ```
+
 10. Consult the **Basic Usage** section of the docs to get started using the features of this package.
 
 .