feat(SEO): enhance product and category JSON-LD with shipping and return policy details

- Added merchant return policy and shipping details to the JSON-LD for both product and category schemas.
- Updated delivery method price to reflect the new shipping rate of 5.90 €.
- Improved localization files to include loading messages for products and updated various translations for consistency.

src/components/profile/DeliveryMethodSelector.js

@@ -17,7 +17,7 @@ const DeliveryMethodSelector = ({ deliveryMethod, onChange, isPickupOnly, cartIt
       name: 'DHL',
       description: isPickupOnly ? (t ? t('delivery.descriptions.notAvailable') : "nicht auswählbar weil ein oder mehrere Artikel nur abgeholt werden können") : 
                    isFreeShipping ? (t ? t('delivery.descriptions.standardFree') : 'Standardversand - KOSTENLOS ab 100€ Warenwert!') : (t ? t('delivery.descriptions.standard') : 'Standardversand'),
-      price: isFreeShipping ? (t ? t('delivery.prices.free') : 'kostenlos') : (t ? t('delivery.prices.dhl') : '6,99 €'),
+      price: isFreeShipping ? (t ? t('delivery.prices.free') : 'kostenlos') : (t ? t('delivery.prices.dhl') : '5,90 €'),
       disabled: isPickupOnly
     },
     {