add reports to RPC server API

**Is your feature request related to a problem? Please describe.**

contender server sessions each hold their own in-memory sqlite DB, and we can't get reports out of them (yet).

**Describe the solution you'd like**

- Add an RPC method `report` that takes a `session_id` and runs a report ranging over all the runs it has executed since it started.
- serve the report over the API in HTML or JSON form (html default; make sure there's an API param in the `report` endpoint to choose this)
- add a report button to the session cabinet in the server dashboard (https://github.com/flashbots/contender/blob/main/crates/cli/src/server/static/index.html)
- pressing the "report" button in the UI should download the report from the API and open it in a new browser tab