Rename twig template folders and files to snake_case

[loevgaard]

The plugin's twig templates use CamelCase folders (and one camelCase filename), a Sylius 1.x-bundle legacy style. Modern Symfony/Sylius convention is snake_case throughout the template tree.

Renames

Current	New
src/Resources/views/Form/theme.html.twig	src/Resources/views/form/theme.html.twig
src/Resources/views/Admin/Order/Show/Payment/_operations.html.twig	src/Resources/views/admin/order/show/payment/_operations.html.twig
src/Resources/views/Admin/Order/Show/Payment/_operationsError.html.twig	src/Resources/views/admin/order/show/payment/_operations_error.html.twig
src/Resources/views/Admin/Order/Show/Payment/_quickpay.html.twig	src/Resources/views/admin/order/show/payment/_quickpay.html.twig

(_operationsError is the one file that is itself camelCase, not just its path.)

Reference sites to update (8)

• src/Controller/Admin/PaymentOperationsAction.php — two render() calls
• src/DependencyInjection/SetonoSyliusQuickpayExtension.php — the prepended form_themes entry and the admin order template config
• tests/Controller/Admin/PaymentOperationsActionTest.php — two path assertions
• tests/DependencyInjection/SetonoSyliusQuickpayExtensionTest.php — two expectations

BC note

Template paths are override points — host apps override via templates/bundles/SetonoSyliusQuickpayPlugin/<same path>, so renaming changes those override paths. All four templates are new in unreleased 2.x (form theme + the #105 operations panel), so the rename is free if it ships before the first stable tag; no UPGRADE-2.0.md entry needed since 1.x shipped no templates at all.