chore: update OpenAPI files and docs.json for Meilisearch v1.39.0

- Fetched latest OpenAPI spec from v1.39.0 release
- Regenerated Mintlify-compatible OpenAPI file
- Added foreign-keys settings routes to docs.json
- Generated changelog for v1.39

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Entire-Checkpoint: 9c68757644a6

Author: qdequele