fix: Dynamic Island, Live Activity errors, background audio stop, CFBundleVersion

Phase 1 — Audio background resilience:
- Remove .mixWithOthers, app takes audio focus for coach cues
- Add AVAudioSession.interruptionNotification handler (re-activates after calls/Siri)
- Add AVAudioSession.routeChangeNotification handler (re-activates on headphone changes)

Phase 2 — Live Activity error surfacing:
- PlayerViewModel: @Published liveActivityError captures auth-denied + request errors
- PlayerView: translucent error banner with dismiss button (non-blocking)

Phase 3 — CFBundleVersion 1→2 in all 4 Info.plist files (match project.yml CURRENT_PROJECT_VERSION: 2)

tabatago-swift/TabataGo/ViewModels/PlayerViewModel.swift

@@ -39,6 +39,7 @@ final class PlayerViewModel: ObservableObject {
     @Published var isComplete: Bool = false
     @Published var showExitConfirmation: Bool = false
     @Published private(set) var completedSession: WorkoutSession? = nil
+    @Published var liveActivityError: String? = nil
 
     // Track info for Live Activity — set by View when music changes
     var currentTrackTitle = ""
@@ -382,7 +383,10 @@ final class PlayerViewModel: ObservableObject {
     // ─── Dynamic Island / Live Activity ─────────────────────────────
 
     func syncActivity(shouldAlert: Bool = false) {
-        guard ActivityAuthorizationInfo().areActivitiesEnabled else { return }
+        guard ActivityAuthorizationInfo().areActivitiesEnabled else {
+            liveActivityError = "Live Activities are disabled in Settings"
+            return
+        }
         guard isRunning else { return }
 
         let isPlayingMusic = (phase == .work || phase == .rest) && isRunning && !isPaused
@@ -449,8 +453,10 @@ final class PlayerViewModel: ObservableObject {
                 attributes: attrs,
                 content: ActivityContent(state: state, staleDate: staleDate)
             )
+            liveActivityError = nil
             observeActivityState()
         } catch {
+            liveActivityError = error.localizedDescription
             print("❌ Failed to start Live Activity: \(error.localizedDescription)")
         }
     }