Implement Animations when the timer reaches 0

[fcFn]

1. Add a sound effect to play when the countdown reaches zero.
2. Implement a confetti animation to celebrate the event start.
3. Provide options in the settings to turn sound and animation on or off.

[fcFn]

Let's go with an easy one, say a gradient flowing over the body (don't forget to accommodate dark theme too) for example. If you'd like to go extra fancy, add those confetti 🎉

Also I would like to have a little bit of accessibility, so we should check for prefers-reduced-motion and only show some very mild animations if this is true.

[fcFn]

Done.