Template exercise can be started from simulation settings modal #1277
Description
When I'm in an exercise template, the button to start the exercise is not visible in the bottom toolbar.
However, the simulated regions modal still contains the "start" button and the server still accepts the respective action, so that an exercise template can be started. Since the timer is also hidden, there is no way to notice that the exercise is already running and an exercise that has been started by accident may be running indefinitely (as long as at least one client joined the exercise).
This leads to patient health, transfers and simulated regions already progressing and exercises created from this template will start at whatever time the template has run instead of at 0:00, which may be confusing during exercise evaluation.