Loading spinner for tasks screen

[jaragunde]

There is currently no feedback on the load operation in the tasks screen. Users don't know whether the selected date is empty or it hasn't finished loading the tasks yet.

Let's add some feedback during the load operation, for example, a spinner with the "loading" message.

[dmtrek14]

We are in the process of rewriting the frontend for tasks. Any outstanding bugs and enhancements for the old interface will be taken into account as we implement the new design.