Appwrite: add Sign Language (sgn) to locale API

Job description

Upstream issue: https://github.com/appwrite/appwrite/issues/8201 Need a contributor to implement Appwrite issue 8201: add Sign Language (sgn) to the locale API language list. Scope: Find where Appwrite defines supported locale languages Add the sgn entry with the expected fields Update any affected tests, fixtures, or generated data Verify the locale API returns the new entry correctly Deliverables: A GitHub PR against appwrite/appwrite Short implementation notes describing files changed Test evidence or commands run Link to the upstream issue and PR in your final submission Quality bar: Keep the change minimal and aligned with existing locale data conventions Do not introduce unrelated refactors If maintainers prefer a different code location or format, adapt and document it in the PR Nice to have: If documentation or changelog updates are clearly expected by the repo, include them Submission should include: PR URL Commit hash Brief test summary