New features: Reward shop sale and nagging whistle

[timergames]

Here's a breakdown of the new features:

Reward Shop Sale (Fixed): I've completely refactored the sale logic. The app was permanently reducing prices instead of offering a temporary discount. Now, the 5% discount is calculated "on-the-fly" when you open the shop, and the correct discounted price is used for purchases. The base price of your rewards will no longer be affected.

Nagging Whistle: The Drill Sergeant won't let you forget. While a task is active, you will hear a "reminder" whistle every 30 minutes in addition to the first one.

"Task Master" Fanfare: On successful task completion, you'll now hear a three-note fanfare (High, Low, Low) that sounds like "Task Mas-ter!"

Gamify your life with Taskmaster