Fix registration 415: send multipart form data with ID images

- addCustomer/addOwner now use FormData with multipart upload
- Front and back ID images appended as FrontIdCarImage/RearIdCarImage
- Registration pages pass idImages.front and idImages.back to API
- Field names mapped to PascalCase for .NET API (FullName, Email, etc.)

app/register/owner/page.js

@@ -132,7 +132,7 @@ export default function OwnerRegisterPage() {
     };
 
     try {
-      const res = await addOwner(payload);
+      const res = await addOwner(payload, idImages.front, idImages.back);
       console.log('[OwnerRegister] addOwner response:', res);
 
       if (res.status === 200 || res.ok) {