feat: challenge submission by Juan

[jbnone]

• Introduces a FastAPI service exposing POST /productionplan on port 8888 with strict Pydantic validation and typed responses.
• Implements a deterministic, cost-based production planner with 0.1 MW granularity, Pmin/Pmax handling, wind availability, and optional CO2 cost for gas-fired units.
• Provides comprehensive error handling with HTTP 422 for infeasible loads and clear validation messages.
• Adds full test suite (schemas, planner, API) ensuring algorithm correctness and API behavior.
• Supplies developer tooling and docs: README with run instructions, Dockerfile for containerization, and example payloads.