Some enterprises do not want their users to be able to `/feedback`.
<img width="395" height="325" alt="image"
src="https://github.com/user-attachments/assets/2dae9c0b-20c3-4a15-bcd3-0187857ebbd8"
/>
Adds to `config.toml`:
```toml
[feedback]
enabled = false
```
I've deliberately decided to:
1. leave other references to `/feedback` (e.g. in the interrupt message,
tips of the day) unchanged. I think we should continue to promote the
feature even if it is not usable currently.
2. leave the `/feedback` menu item selectable and display an error
saying it's disabled, rather than remove the menu item (which I believe
would raise more questions).
but happy to discuss these.
This will be followed by a change to requirements.toml that admins can
use to force the value of feedback.enabled.
gt-oai
5b5a5b92b5