fix(session): clear stale error state when signaling starts reconnecting

When SignalingConnecting fires after a failed connection attempt,
lastSignalingClientConnectError and lastSignalingDisconnectCode were
not cleared. This left the status stuck on connectError/connectIssue
('Connection error' / 'Connection issue') even though a fresh connect
attempt was already in progress.

After this fix, SignalingConnecting resets all stale error fields so
the status correctly shows inProgress ('Connection in progress') for
the duration of the reconnect.

Author: SERDUN

lib/features/call/bloc/call_bloc.dart

@@ -627,7 +627,9 @@ class CallBloc extends Bloc<CallEvent, CallState> with WidgetsBindingObserver im
       state.copyWith(
         callServiceState: state.callServiceState.copyWith(
           signalingClientStatus: SignalingClientStatus.connecting,
+          lastSignalingClientConnectError: null,
           lastSignalingClientDisconnectError: null,
+          lastSignalingDisconnectCode: null,
         ),
       ),
     );