Lightweight worker for static exports

At present, static exports currently include a full worker that is capable of doing the heavy lifting you would normally have with an app.

This should either be stripped back to a minimal worker that only handles things like image optimisation and/or middleware, or removed altogether.

We should ensure that we support running static exports without the cloudflare vite plugin as part of this.

Start by tracing how static exports create and invoke the worker, then inspect the Cloudflare Vite plugin integration. Define whether the worker should be reduced to image optimisation and middleware or removed, and verify that static exports run without the plugin.

Written by the indexing model from the issue text.