This is not right. A systemd timer requires corresponding service file but you do not enable the service. You only enable the timer. Therefore there should be no Requires=sauvED.timer and neither [Install] section nor WantedBy= (maybe in some special case but I have never used it).
If you have [Install] in the service and you enable the service then the service starts as soon as your computer starts which means the timer is pointless.
Arch wiki is a good reference for the systemd timers.
Not timer.enable/timer.disable more like 2 timers exec script/killall script. But then you have to solve a problem how to gracefully kill the scipt.
Timer.enable and timer.disable only set a trigger condition. So if enabled then the service will run when the system clock reach OnCalendar=*-*-* 11:55:00 and when you call systemctl disable SauveED.timer it will not trigger next day at 11:55:00 but also it will not kill already running SauveED.service.
But I think this may be an XY-problem.
What is running in your script that has to start on a precise time (with timer) and stop at a different time? I would assume a normal condition for a script to stop is when all the work is done. Having a timestamp for a script termination is unusual for me.
I would also recommend to use type oneshot.
[Service]
Type=oneshot
If you do not specify type then it is Type=simple. The advantage of oneshot is that it is blocking and you can get some info whether the script is running or returned with an error by running systemctl status sauvED.service. And you should be able to kill the script by also calling systemctl stop sauvED.service.