Interval Timer | HIIT Training

Wear OS:
- More reliable background countdown – the timer keeps running even when the screen turns off.
- The screen wakes up automatically at every phase change (Prepare → Train → Rest).
- New settings screen with sound mode, volume slider and a wake-screen-on-transition toggle.
- Heart rate and calorie indicators while you train.

Mobile:
- In-app update prompt on launch so you always run the latest version.
- Edge-to-edge layout polish on the timer and settings screens.