feat: index and filter content by languages

Adds basic multilanguage support by sending the canonical and available languages for an item to vragen.ai. We do this by only submitting the canonical language for indexing and updating the canonical's metadata when a translation is indexed.

Then based on this information we can reconstruct a proper item ID with the desired language. Depending on the fallback setting we either only show content in the preferred language or we fallback to the canonical language of the item.

Closes #3559026