Add bot reviews and ratings

## Description
Eventually support the rating/review concepts already present in the design direction.

### Acceptance criteria
- one review per account per bot
- editable reviews
- abuse/report flow
- aggregate rating calculated server-side
- bots cannot self-review through owner accounts without a defined policy

> [!NOTE]
> This issue should be done after the moderation infrastructure.

Start by reading the existing design direction for rating and review concepts, then inspect the moderation infrastructure because this issue is explicitly dependent on it. Map how accounts, bots, reviews, abuse reports, and server-side aggregates are represented; done means the acceptance criteria are implemented, including the unresolved self-review policy.

Written by the indexing model from the issue text.