Replace local database_api sync client with generated package

- Import DatabaseApi from database_api.database_api_client_sync instead of local sync_api.py
- Delete local sync_api.py (no longer needed, using generated client)
- Update type imports to use database_api_description module
- Add hiveio-database-api as dependency in pyproject.toml

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>