Redesign workout live activity with circular timer ring, phase icons, and smoother updates

- Add CountdownRing with real-time arc progress on lock screen
- Replace generic dots with phase-specific SF Symbols (flame, snowflake, etc.)
- Remove horizontal progress bar in favor of round counter text
- Increase Dynamic Island expanded font sizes for better visibility
- Increase live activity sync frequency from 5s to 1s for smoother arc updates
- Add pause/resume button via TogglePauseIntent AppIntent
- Remove AlertConfiguration to silence notification sounds on updates

tabatago-swift/TabataGo/Models/WorkoutActivityAttributes.swift

@@ -40,6 +40,7 @@ struct WorkoutActivityAttributes: ActivityAttributes {
         var exerciseName: String
         var phase: WorkoutPhase
         var phaseEndDate: Date
+        var phaseDuration: TimeInterval
         var roundCurrent: Int
         var roundTotal: Int
         var heartRate: Double