update public events listing

[tenkus47]

Summary

The Public Events API should use English metadata as a fallback when the selected language is unavailable.

Tasks

• Check whether metadata exists for the user’s selected language.
• Return metadata in the selected language when available.
• If no metadata is available in the selected language, return the English (en) metadata.
• Ensure the event is not excluded simply because the selected-language metadata is missing.
• Add tests for language fallback behaviour.

Expected Behaviour

For example, when the selected language is bo:

• If Tibetan metadata exists, return the Tibetan metadata.
• If Tibetan metadata does not exist, return the English metadata.
• If neither Tibetan nor English metadata exists, return the event with empty or NULL metadata fields, according to the API response standard.

Fallback Logic

selected language → English (`en`) → empty/null metadata