switch to create_app from http_server

fix step format, add tasks endpoint back

fix create_fastapi_app call remove env_name

use openenv base classes and fix yaml format to match working submissions

add grader endpoint

pin openenv-core version to force reinstall

add grader_fn to tasks endpoint

revert to working server

use openenv core base classes

commit missing openenv.yaml and server.py changes

fix grader serialization and tasks endpoint

fix /tasks endpoint format for validator

Fix server entrypoint packaging and align environment docs