F-097 — Implementer evidence

Fixed the admin catch-all POST proxy: it no longer sends Content-Type: application/json when the request has no body.
This allows POST /api/products/:id/generate-seo to reach the backend; previously Fastify rejected the empty request with FST_ERR_CTP_EMPTY_JSON_BODY (400).
Rebuilt and restarted the production monolith.

Validation:

Admin production build: exit 0
Authenticated /api/admin/settings: HTTP 200
Authenticated empty-body SEO request: HTTP 422 AI_NOT_CONFIGURED with actionable message (instead of HTTP 400)