Add Symfony admin configuration stack (controller, form, service, routing, whitelist)

[CySSoO]

Motivation

• Provide a modern Symfony-based admin UI for Everblock configuration while preserving backward compatibility with legacy admin controllers.
• Encapsulate configuration logic into a service to prepare for progressive migration away from HelperForm/ObjectModel usage.
• Ensure all new Symfony files are whitelisted in config/allowed_files.php so the module cleanup mechanism does not remove them.

Description

• Add a Symfony admin controller: src/Controller/Admin/EverblockConfigurationController.php that renders and processes a Symfony form and redirects back on success. It uses EverblockConfigurationManager and TranslatorInterface.
• Add a Symfony form type: src/Form/Type/EverblockConfigurationType.php using TranslateType, TextType and IntegerType with validation constraints for key configuration inputs.
• Add a configuration service: src/Service/Configuration/EverblockConfigurationManager.php which uses ConfigurationAdapter, ShopContext and LanguageDataProvider to read/update multishop and multilanguage configuration safely.
• Add routing and DI wiring: created config/routes.yml (route everblock_admin_configuration) and updated config/services.yml to autowire the new Controller, Form and Service/Configuration namespaces. The route includes _legacy_controller/_legacy link to preserve permissions/legacy tab behavior.
• Whitelist new files: updated config/allowed_files.php to include all newly added files and the new route file plus the Twig template at views/templates/admin/symfony/configuration.html.twig.
• Add index/guard files for new directories: src/Controller/index.php, src/Controller/Admin/index.php, src/Form/index.php, src/Form/Type/index.php, src/Service/Configuration/index.php, and a Twig template for the new admin form.

Testing

• Automated tests: none executed for this change (no unit or integration tests were run in this rollout).
• Note: The change is limited to adding files, wiring services/routes and updating the whitelist; manual verification of files creation and config/allowed_files.php updates was performed during the rollout.

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Codex Task