- Integrate tonic-health for gRPC service health monitoring
- Add etcd-based service registration with automatic keep-alive
- Implement dynamic configuration loading from etcd with fallback
- Remove external dependencies from docker-compose for simplified deployment
- Refactor service registration logic with improved lease management
- Add health service to gRPC server with serving status reporting
- service/auth/login.rs: extract auth_find_user() helper combining
username + email lookup, reducing login flow from 5 levels to 3
- etcd/register.rs: extract run_keep_alive_stream() and
renew_lease_and_reregister() from spawn_keep_alive(), reducing
max nesting from 7 levels to 3