Add systemone API for SI

[ShivaniKumar1]

Summary

• add POST /v1/systemone, a serverless, pass-through evaluation endpoint for TypeSafe AI's Jev model, under the existing Serverless Inference tag
• request/response schema matches inference-proxy's live contract (internal/api/typesafe/openapi.yaml): state + model + a questions map of noul/choice/score types in, answers + usage out

Validation

• source and bundled Spectral lint: 0 new errors
• confirmed every $ref in the new files resolves
• confirmed /v1/systemone is already present in production's edge/gateway allowlist, so this isn't documenting an unroutable endpoint
• confirmed via inference-proxy's current implementation that the request and response schemas match what the service actually accepts and returns

[SSharma-10]

LGTM