ver. 0.303: Fix attribute display collision + product preview button

Fix: product attributes with the same sort order value were overwriting
each other in getProductAttributes(), causing only one attribute to
display on the frontend. Now uses usort() with sequential keys.

New: Preview button in product edit form opens product page in new tab.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

autoload/admin/ViewModels/Forms/FormAction.php

@@ -56,6 +56,22 @@ class FormAction
         );
     }
 
+    /**
+     * Predefiniowana akcja Podgląd (otwiera w nowej karcie)
+     */
+    public static function preview(string $url, string $label = 'Podgląd'): self
+    {
+        return new self(
+            'preview',
+            $label,
+            $url,
+            null,
+            'btn btn-info',
+            'link',
+            ['target' => '_blank']
+        );
+    }
+
     /**
      * Predefiniowana akcja Anuluj
      */