Evaluation UI: Loading screen

[AkhileshNegi]

Is your feature request related to a problem?

When clicking 'View Results' on evaluation runs with 100+ items, the screen takes a long time to populate results. The data is fetched
from Langfuse, saved to the database, then displayed in the UI. Sometimes the request times out with a 502 error, resulting in poor
UX.

Describe the solution you'd like

• Add a loading screen with descriptive text while results are being fetched
• Run the fetch operation in the background
• Increase timeout threshold to prevent 502 errors on large result sets

Alternative
Explore langfuse APIs and fetch 25-50 items per page instead of 100+ at once. This eliminates timeout risk and can show some results initially

Screenshots