Fix/update at

[DeleMike]

Contributor checklist

• This pull request is on a separate branch and not the main branch
• I have ran the ./pre-commit executable as well as make lint and have fixed all reported issues

---

Description

This PR fixes the issue as stated in #104.

1. Old data backups on Toolforge are removed. Each deployment moves the current SQLite packs into a packs/sqlite.backup.<date> folder, and these were never deleted. The deploy step now keeps only the two most recent backups, so there's always the one just made plus one older for a rollback.

2. updated_at now matches data-version. Scribe-Server always set updated_at in the GET /api/v1/data/{lang} response to the date of the API request. This was set during my initial development of the API. GET /api/v1/data-version/{lang} already has the correct dates, which client apps can ping to know whether they need to get new data. This PR sets updated_at to the most recent of those data-version dates, so both endpoints agree.

   For example, for English:

   • data-version: nouns 2026-09-30, verbs 2026-09-28, profanity 2026-10-01
   • updated_at: 2026-10-01 (previously the date of the request)

Testing

• Added unit tests for picking the most recent date (database/versions_test.go).
• Ran the server locally and checked that updated_at matches the newest data-version date for en, de and ru.
• Tested the backup cleanup on sample backup folders: only the two newest are kept, and packs/sqlite isn't touched.

Related issue

• closes updated_at is always the request date, and Toolforge keeps every data backup #104

[andrewtavis]

praise: This all looks great and makes total sense, @DeleMike! Thanks for deriving the issue here and sending along the fix! 😊

[DeleMike]

Thanks! I will now run the process :)