Refactoring code to use the "visibilitychange" event

Using the "visiblitychange" event instead of relying on a "trick" related to RAF being disabled when a window is not open allows us to have cleaner code.
Bonus: the recursive call to "setTimeout" is gone, so the stacktrace growing indefinitely is gone too.
This should make the application a bit more stable.

front/src/Phaser/Login/EnableCameraScene.ts

@@ -247,7 +247,6 @@ export class EnableCameraScene extends Phaser.Scene {
 
     update(time: number, delta: number): void {
         this.soundMeterSprite.setVolume(this.soundMeter.getVolume());
-        mediaManager.updateScene();
 
         const middleX = this.getMiddleX();
         this.tweens.add({