WALDO UI lag when adding a new Site (Sites tab reload takes ~30–40s even on fast internet)

[pearl-mallick]

Description
Even with a strong, stable internet connection (normal speeds for other web apps), WALDO feels laggy. The most noticeable case is adding a new site in the Sites tab: after submitting, the page reloads and takes ~30–40 seconds before the new site appears.
This is happening consistently and makes the Sites workflow feel blocked, and when adding many sites (see Greg’s ticket on batch sample upload for sites), this is time consuming.
Steps to Reproduce

1. Open WALDO
2. Go to Sites tab
3. Add a new site (enter name / required fields)
4. Submit/save
5. Observe the page reload + long wait before the site is added/visible
   Actual Result
   After clicking save, the page reloads and takes 30–40 seconds to complete (on my Sequoia 15.2 Macbook pro, Chrome browser, on the Harvard vpn)
   The new site does not appear until the reload finishes.
   Frequency: Every time