fix: resolve Pyrefly linter errors - add search-path config and type guards

last 0 and 1 error update

fix: add pyright extraPaths to resolve IDE import warnings for models, grader, tasks, server.environment

fix: strictly pin dependencies in pyproject.toml and use python:3.10-slim to bypass HF docker image cache rate limits

Add openenv-core dependency and uv.lock

project upload