[bug] No loading visual feedback when opening map popups

[pandafy]

Originally posted by @nemesifier in #688 (review)

Describe the bug
When opening a map point popup on slow internet connection, there is no visual indication that content is loading. This lack of feedback can be confusing for users, as it appears that nothing is happening during the loading operation.

Steps To Reproduce

1. Open the monitoring map interface.
2. Enable network throttling (e.g., "Slow 3G") in your browser's developer tools.
3. Click on a map point to open its popup.
4. Observe that there is no visual feedback indicating that loading is in progress.

Expected behavior
There should be a visible loading indicator or feedback when a map popup is in the process of loading data, especially under slow network conditions.