ver. 0.302: REST API product variants, attributes dictionary, attribute filtering

- Add variant CRUD endpoints (variants, create_variant, update_variant, delete_variant)
- Add dictionaries/attributes endpoint with multilingual names and values
- Add attribute_* filter params for product list filtering by attribute values
- Enrich product detail attributes with translated names (attribute_names, value_names)
- Include variants array in product detail response for parent products
- Add price_brutto validation on product create
- Batch-load attribute/value translations (4 queries instead of N+1)
- Add 43 new unit tests (730 total, 2066 assertions)

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

autoload/api/ApiRouter.php

@@ -92,13 +92,15 @@ class ApiRouter
             },
             'products' => function () use ($db) {
                 $productRepo = new \Domain\Product\ProductRepository($db);
-                return new Controllers\ProductsApiController($productRepo);
+                $attrRepo = new \Domain\Attribute\AttributeRepository($db);
+                return new Controllers\ProductsApiController($productRepo, $attrRepo);
             },
             'dictionaries' => function () use ($db) {
                 $statusRepo = new \Domain\ShopStatus\ShopStatusRepository($db);
                 $transportRepo = new \Domain\Transport\TransportRepository($db);
                 $paymentRepo = new \Domain\PaymentMethod\PaymentMethodRepository($db);
-                return new Controllers\DictionariesApiController($statusRepo, $transportRepo, $paymentRepo);
+                $attrRepo = new \Domain\Attribute\AttributeRepository($db);
+                return new Controllers\DictionariesApiController($statusRepo, $transportRepo, $paymentRepo, $attrRepo);
             },
         ];
     }