Make AccountValueResolver support concrete account entity classes

[javihgil]

Problem

AccountValueResolver only resolves arguments typed exactly as AccountInterface.

Current code:

• src/Request/AccountValueResolver.php:26 returns early unless $argument->getType() === AccountInterface::class

Impact

This breaks the common Symfony case where controllers type-hint a concrete account entity class implementing AccountInterface.

The resolver works for the interface but not for the actual entity classes most applications use.

Expected behavior

• resolve arguments typed as AccountInterface
• also resolve arguments typed as concrete classes implementing AccountInterface
• keep the current route param / repository lookup behavior
• add unit coverage for both interface and concrete-class arguments