format: fix psr12 style issues

phpcbf auto-fixes: string concatenation spacing, single-line class braces, closing brace placement.

backend/app/User/User.php

@@ -10,7 +10,8 @@ class User
         private int $id,
         private EmailAddress $email,
         private string $passwordHash,
-    ) {}
+    ) {
+    }
 
     public function getId(): int
     {