plg: Public-facing Simulator API (Try without signup)

[keirsalterego]

Goal

Allow prospective customers to test the Vyrox AI on their own payloads before signing up.

Scope

• Create a read-only endpoint that accepts a JSON payload and returns the deterministic Heuristic score and LLM triage reasoning.
• Does not persist to the database or trigger Discord notifications.

OpSec Mandate

Ensure LLM usage is strictly rate-limited and scoped to a hardcoded 'demo' tenant ID to prevent token exhaustion attacks.