Missing loading indicators for pending requests

[ankitsejwal]

Problem

pgweb lacks loading spinners/indicators during API requests, making it appear unresponsive to users.

Impact

• Users can't tell if the app is processing or hung
• Particularly problematic for slow foreign table operations
• Poor user experience during query execution and data loading

Expected Solution

Add loading indicators for:

• Table data fetching
• Query execution
• Schema/object loading
• Table information requests

Users should see visual feedback that requests are in progress.