Look up a market by its slug for short URL support. Returns the market with its condition_id for redirect purposes. Useful for /go/[slug] short URLs for easy sharing on X/Twitter.
Also handles condition_id inputs gracefully — the frontend sometimes sends condition_ids to this endpoint (e.g., from generateMetadata parallel fetches). If the input looks like a condition_id (starts with 0x), we proxy to the condition_id lookup path instead of 404ing.
Cache-first: Checks Redis slug→condition_id mapping before DB.
Successful Response