Add origin auth header to images

We would like to track how many requests were done by each service - nova, talisman, kodadot, indexers.

I would imagine that as simple KV so we have some usable estimates.

The issue names no files or tests. Start by locating the image request handling and the Cloudflare Workers KV configuration, then trace how requests can identify nova, talisman, kodadot, and indexers. Done means image requests carry the intended origin authentication information and request counts are recorded per service in a usable key-value structure.

Written by the indexing model from the issue text.