fix: use valid HF Space colorTo value (blue not cyan)

feat(v2): execution-grounded rewards via DuckDB -- the key differentiator

chore(infra): add Dockerfile, dependencies, and build config

feat(inference): add OpenEnv-compliant inference script

feat(server): add FastAPI server with all OpenEnv endpoints

feat(core): add grader and SQLOptimEnv environment class

feat(data): add Pydantic models and task definitions

feat: add OpenEnv spec, README, and gitignore

initial commit