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/i18n/locales/el/product.js

@@ -25,6 +25,7 @@ export default {
   "pickupPrice": "Τιμή παραλαβής: €19.90 ανά μοσχεύμα.",
   "consistsOf": "Αποτελείται από:",
   "loadingComponentDetails": "{{index}}. Φόρτωση λεπτομερειών συστατικού...",
+  "loadingProduct": "Φόρτωση προϊόντος...",
   "individualPriceTotal": "Συνολική τιμή μεμονωμένων:",
   "setPrice": "Τιμή σετ:",
   "yourSavings": "Η εξοικονόμησή σας:",