Add a button to pause the polling cycle for logs

If one is searching for a specific log entry, one may want to pause polling when one finds it, so that new logs don't cause what was found to scroll. We can add a simple iconbutton next to the refresh button to pause polling. Along with this should be a "play" button to restart polling. Play should be disabled while polling is active. When polling is paused, the pause button switches state to inactive, and the play button to active, making clear their purpose.

Start by locating the log polling cycle and the existing refresh button in the frontend. Trace how polling state affects log scrolling, then verify that pause and play controls switch states correctly, with play disabled during active polling and pause inactive while paused.

Written by the indexing model from the issue text.