Release v1.3.1 - Bug fixes, documentation improvements, and CI enhancements

See RELEASE_NOTES_1.3.1.md for full details.

Key highlights:
- Fixed file upload size limits (10MB → 100MB)
- Added CORS headers to error responses
- Reduced retry log noise during chunk processing
- Added Claude Code GitHub Actions integration
- Added MCP integration documentation
- Improved SurrealDB persistent storage in docker-compose docs
- CI workflow optimizations