fix: handle ATProto DotDict responses and add live integration tests
- Convert ATProto model objects (DotDict) to plain dicts in get_record()
and list_records() methods for consistent downstream handling
- Add pytest markers for 'network' and 'slow' tests in pyproject.toml
- Add live atmosphere integration test for real ATProto interactions
- Ignore testing.env credentials file
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>