Adjustment Shopware Plugin

# PHP Developer Task Description – Update Custom Premium Items Logic for Shopware 6.7.10.1 We currently use a custom modification for the Premium Items plugin in Shopware 6 that changes how premium products are activated. ## Current Behavior Normally, the plugin calculates premium item eligibility based on the regular product selling price. We added a custom adjustment so that: * If the normal selling price of a product is `0.00 €` * The system should instead use the product’s **strike-through price / list price** (“Streichpreis”) as the calculation base * This calculated value is then used to determine whether premium products are unlocked This customization worked in previous Shopware versions but must now be reviewed and updated for compatibility with: * Shopware `6.7.10.1` * Premium Items Plugin by Bartosz Sosna [Premium Items Plugin Demo](https://bartosz.sosna.com.de/demo-premium-items.html?utm_source=chatgpt.com) ## Required Task The developer should: 1. Analyze the existing custom code modification 2. Check compatibility with Shopware `6.7.10.1` 3. Update the implementation so it continues to work correctly with the current plugin version 4. Ensure the premium item calculation uses: * the normal sales price when available * but automatically falls back to the strike-through/list price if the sales price equals `0.00 €` 5. Verify that premium products are correctly unlocked in frontend/cart scenarios 6. Ensure the customization is update-safe and cleanly implemented ## Important Notes * The existing logic already exists in the project and should not be rebuilt from scratch unless necessary * The goal is to restore and stabilize compatibility after Shopware/plugin updates * Please document all modified files and changes * The solution should follow Shopware 6 best practices and avoid core modifications if possible ## Expected Result Premium item thresholds and unlock logic must continue functioning correctly even when products have a sales price of `0.00 €`, by using the strike-through/list price as fallback for calculation purposes.