## Context
Related BE PR: https://github.com/supabase/platform/pull/32693
Add support to remove the custom domain add-on when deleting a custom
domain after the custom domain is activated.
<img width="411" height="310" alt="image"
src="https://github.com/user-attachments/assets/23d57fc0-f760-42d4-8383-480ff2b2ec5a"
/>
We previously had this behaviour by default to address some customer
feedback RE confusion that they were still being charged for custom
domain add-on despite deleting the custom domain, but not removing the
add-on.
However this was a bit of confusing UX (RE deleting the add-on
implicitly), so this makes the deleting of the custom domain add-on an
explicit action instead.
## To test
- [ ] Set up custom domain on a project
- [ ] Trying deleting the custom domain after activating _without_
removing the add-on
- [ ] Trying deleting the custom domain after activating _with_ removing
the add-on
