feat(gateway): add debug logging with file storage and retention
feat(gateway): add audit logging for user actions
feat(gateway): add request ID tracking and rate limit headers
feat(gateway): add model aliases and load balancing strategies
feat(gateway): add config hot-reload via SIGHUP
feat(gateway): add CORS support
feat(gateway): add data export API and dashboard endpoints
feat(gateway): add dashboard pages for audit and debug logs
feat(gateway): add concurrent request limiting per token
feat(gateway): add streaming timeout support
feat(gateway): add migration support for new schema fields
