Features: 1) Update vendor object creation to use fully qualified module path;

Fixes: 1) Correct path for vendor module resolving import issue;

Extra: 1) Improve readability of vendor initialization logic;

engine/core/signals.py

@@ -173,7 +173,8 @@ def process_order_changes(instance: Order, created: bool, **kwargs: dict[Any, An
                     )
 
                     vendor = create_object(
-                        f"core.vendors.{vendor_name}", f"{vendor_name.title()}Vendor"
+                        f"engine.core.vendors.{vendor_name}",
+                        f"{vendor_name.title()}Vendor",
                     )
 
                     vendor.buy_order_product(order_product)  # type: ignore [attr-defined]