Issue Free Key

Self-serve FREE API key (data-product plan T1.2).

Request Body:

• email: required; one key per email
• use_case: optional, max 500 chars (mirrored into the waitlist as type "free_key")

Returns {"key": ...} exactly once. A repeat request for the same email is 409 and carries only the existing key's 8-char prefix. FREE key = delayed counters (FREE_COUNT_DELAY_SEC), current event only, last 15 posts, 100 req/h keyed on the key. Rate limit on this route: 5 issues per hour per IP. No authentication required.