Fix YouTube relay instabile e timer LIVE a zero in app

ffmpeg: probesize/analyzeduration su _air, restart più rapido e avvio relay
al go_live. App: sincronizza started_at dal server e fallback al passaggio live.

Co-authored-by: Cursor <cursoragent@cursor.com>

mobile/lib/features/camera_mode/camera_screen.dart

@@ -41,6 +41,7 @@ class _CameraScreenState extends ConsumerState<CameraScreen> {
   static const _previewKey = ValueKey<String>('camera_streaming_preview');
 
   Timer? _elapsedTimer;
+  Timer? _sessionSyncTimer;
   Timer? _telemetryTimer;
   Timer? _statsTimer;
   Timer? _scorePullTimer;
@@ -75,6 +76,9 @@ class _CameraScreenState extends ConsumerState<CameraScreen> {
             );
       }
     });
+    _sessionSyncTimer = Timer.periodic(const Duration(seconds: 15), (_) {
+      unawaited(_syncSessionStartedAt());
+    });
     _telemetryTimer = Timer.periodic(const Duration(seconds: 10), (_) => _sendTelemetry());
     _statsTimer = Timer.periodic(const Duration(seconds: 30), (_) => _fetchStats());
     _scorePullTimer = Timer.periodic(const Duration(seconds: 2), (_) {
@@ -263,6 +267,20 @@ class _CameraScreenState extends ConsumerState<CameraScreen> {
     } catch (_) {}
   }
 
+  /// Il server imposta `started_at` solo al primo go_live; sincronizza per il timer LIVE.
+  Future<void> _syncSessionStartedAt() async {
+    final current = ref.read(sessionProvider).session;
+    if (current == null || current.startedAt != null || !current.isLive) return;
+    try {
+      final fresh = await ref.read(apiClientProvider).fetchSession(widget.sessionId);
+      if (!mounted || fresh.startedAt == null) return;
+      ref.read(sessionProvider.notifier).setSession(
+            fresh,
+            match: ref.read(sessionProvider).match,
+          );
+    } catch (_) {}
+  }
+
   Future<void> _lockOrientations() async {
     await SystemChrome.setPreferredOrientations([
       DeviceOrientation.landscapeLeft,
@@ -497,6 +515,7 @@ class _CameraScreenState extends ConsumerState<CameraScreen> {
   @override
   void dispose() {
     _elapsedTimer?.cancel();
+    _sessionSyncTimer?.cancel();
     _telemetryTimer?.cancel();
     _statsTimer?.cancel();
     _scorePullTimer?.cancel();