## Context
Related to dashboard scalability
Previous PR: https://github.com/supabase/supabase/pull/42856
Note: Changes are all feature flagged still and I'm still not entirely
convinced with the current UX
Will iterate as as go along, and only make this publicly available when
we're satisfied with the behaviour
Adds a "Dashboard preference" section to the project settings
<img width="265" height="740" alt="image"
src="https://github.com/user-attachments/assets/6ce1aa19-26c2-47c6-a9c4-595137266631"
/>
In which users can then select which database they'd like to use for
read queries run from the dashboard
Note: Everything is local storage for now, but we'd need middleware
support if we want to make this setting persist for all users on the
project
<img width="791" height="434" alt="image"
src="https://github.com/user-attachments/assets/e651d6d9-fed4-4da4-b552-c9f93f8d46d3"
/>
Added a dialog as well to further explain what this implies
<img width="610" height="312" alt="image"
src="https://github.com/user-attachments/assets/0aa957af-cb51-476f-aa79-8948a7cbe5ae"
/>
## To test
- Choosing a replica in dashboard preferences will only affect the table
editor as thats the only place that's set up so far to use a replica for
read queries (I'll need to follow up for other parts of the dashboard in
subsequent PRs)
Joshen Lim