Per-product modal trigger: add button image/label support and DB self‑heal checks

[CySSoO]

Motivation

• Enable merchants to customize the product modal trigger per product by using a button image or custom label instead of the default trigger.
• Ensure the module self-heals databases by adding checks for the newly introduced modal button columns so upgrades/installations add missing fields automatically.

Description

• Add persistent fields for the per-product trigger by introducing button_file and button_label columns in sql/install.php and model properties in models/EverblockModal.php with multilingual support via button_label.
• Extend the admin product UI in views/templates/admin/productModal.tpl to accept a Button label and a Button file with preview and delete controls, and expose related Smarty variables from the module backend.
• Refactor the admin uploader script views/js/product-modal.js to support two upload targets (modal and button) and send a target parameter for uploads/deletes.
• Update backend handlers in everblock.php to accept the target parameter in ajaxProcessProductModalFile, handle upload/delete for both file and button_file, and persist transfer payloads from product save logic (including deletion handling and file cleanup).
• Render the custom trigger in the front office via views/templates/hook/modal.tpl to show an image (with views/css/everblock.css styles) when button_file exists or fallback to button_label text, preserving existing modal behavior.
• Add schema self-heal checks in src/Service/EverblockTools.php::checkAndFixDatabase() to add missing button_file to everblock_modal and button_label to everblock_modal_lang when needed.

Testing

• No automated tests were executed for these changes.

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Codex Task