feat: bulk delete in product archive (v0.327)

- Add bulk_delete_permanent() endpoint (POST ids[], returns JSON)
- Checkbox column + bulk action bar with count label
- Select-all in table header, confirmation dialog before delete
- 2 new tests for bulk_delete_permanent method signature

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

tests/Unit/admin/Controllers/ProductArchiveControllerTest.php

@@ -53,4 +53,15 @@ class ProductArchiveControllerTest extends TestCase
         $this->assertCount(1, $params);
         $this->assertEquals('Domain\Product\ProductRepository', $params[0]->getType()->getName());
     }
+
+    public function testHasBulkDeletePermanentMethod(): void
+    {
+        $this->assertTrue(method_exists($this->controller, 'bulk_delete_permanent'));
+    }
+
+    public function testBulkDeletePermanentMethodReturnType(): void
+    {
+        $reflection = new \ReflectionClass($this->controller);
+        $this->assertEquals('void', (string)$reflection->getMethod('bulk_delete_permanent')->getReturnType());
+    }
 }