feat: add submission validator script and GRPO training notebook, and update Python version requirement to >=3.10

feat: Add full OpenEnv compliance

fix: add 'server' entry point for OpenEnv validator

fix: add server entry point and pyproject scripts for OpenEnv validator

refactor: update Dockerfile and pyproject.toml for dependency management; remove FastAPI server implementation

feat: add server script entry point and create uv.lock for dependency management

Enhance Dockerfile and project structure for GridMind-RL