feat: move HealthKit permission to onboarding, remove HR write

- Add .health step to onboarding between frequency and ready
- HealthStep with non-blocking permission flow (Not Now skips)
- Remove requestAuthorization() from PlayerViewModel.startWorkout()
- Guard live session start with isAuthorized check
- Remove heart rate write from HealthKit authorization popup
- Remove HR sample writing from saveWorkout (now without permission)
- Add L10n keys: healthAccess, healthAccessSubtitle, allowHealthAccess, notNow
- Add EN/DE/ES/FR translations
- Track permission decisions through analytics
- Entry animation on HealthStep (fade-in + slide-up)

HealthKit permission is now asked once during onboarding,
never interrupting workouts again.

tabatago-swift/TabataGo/ViewModels/PlayerViewModel.swift

@@ -137,7 +137,11 @@ final class PlayerViewModel: ObservableObject {
 
         // Start HealthKit live session
         Task {
-            try? await HealthKitService.shared.requestAuthorization()
+            guard await HealthKitService.shared.isAuthorized else {
+                print("[PlayerVM] HealthKit not authorized — skipping live session")
+                return
+            }
+
             liveSession.onHeartRateUpdate = { [weak self] hr in
                 Task { @MainActor in self?.heartRate = hr }
             }