Stabilizza live YouTube/RTMP e fix crash rotazione mobile.

Pipeline YouTube con relay, overlay e publisher sync lato backend; fix GL pauseGlDuringRotation su Android per evitare crash in rotazione durante lo streaming Flutter.

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

mobile/lib/providers/session_provider.dart

@@ -44,7 +44,12 @@ class SessionNotifier extends StateNotifier<SessionState> {
   SessionNotifier() : super(const SessionState());
 
   void setSession(StreamSession session, {MatchModel? match}) {
-    state = state.copyWith(session: session, match: match);
+    final prevId = state.session?.id;
+    state = state.copyWith(
+      session: session,
+      match: match,
+      elapsed: prevId != null && prevId != session.id ? Duration.zero : state.elapsed,
+    );
   }
 
   void updateYoutubeLinks({
@@ -111,8 +116,6 @@ class SessionNotifier extends StateNotifier<SessionState> {
         state = state.copyWith(cameraDevice: device);
         return;
       }
-      final startedAt = s.startedAt ??
-          ((incoming == 'live' || incoming == 'reconnecting') ? DateTime.now() : null);
       state = state.copyWith(
         session: StreamSession(
           id: s.id,
@@ -129,7 +132,7 @@ class SessionNotifier extends StateNotifier<SessionState> {
           privacyStatus: s.privacyStatus,
           qualityPreset: s.qualityPreset,
           targetBitrate: s.targetBitrate,
-          startedAt: startedAt,
+          startedAt: s.startedAt,
           disconnectionCount: s.disconnectionCount,
           score: s.score,
           devices: s.devices,