AI/Infra: Implement dynamic engine depth scaling based on opponent ELO

[chinweobtagaz]

Description

If a 1200 ELO player plays against Stockfish level 20, they will lose every time, resulting in a poor user experience. The engine must scale its difficulty dynamically.

What Needs to be Done

• Map human ELO ratings to engine depth and skill parameters.
• Implement an API middleware that dynamically sets the engine's config based on the matchmaking payload.
• Adjust parameters like Skill Level, MultiPV, and Depth dynamically.

Acceptance Criteria

• Engine plays at a roughly equivalent ELO to the requesting user.
• Lower skill levels result in faster compute times (saving server resources).
• The transition in difficulty feels natural, not just random blundering.