Phase 2 scaffold: mitra online status & pairing logic

Add mitra online/offline status with heartbeat-based auto-offline,
customer-mitra pairing via Valkey pub/sub blast, session management,
and control center dashboard with real-time stats.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mitra_app/lib/core/status/status_bloc.dart

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+import 'dart:async';
+import 'package:equatable/equatable.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import '../api/api_client.dart';
+
+// Events
+abstract class StatusEvent extends Equatable {
+  @override
+  List<Object?> get props => [];
+}
+
+class StatusLoadRequested extends StatusEvent {}
+class ToggleOnline extends StatusEvent {}
+class ToggleOffline extends StatusEvent {}
+class HeartbeatTick extends StatusEvent {}
+class AppPaused extends StatusEvent {}
+class AppResumed extends StatusEvent {}
+
+// States
+abstract class StatusState extends Equatable {
+  @override
+  List<Object?> get props => [];
+}
+
+class StatusInitial extends StatusState {}
+
+class StatusLoaded extends StatusState {
+  final bool isOnline;
+  StatusLoaded({required this.isOnline});
+  @override
+  List<Object?> get props => [isOnline];
+}
+
+class StatusLoading extends StatusState {}
+
+class StatusError extends StatusState {
+  final String message;
+  StatusError(this.message);
+  @override
+  List<Object?> get props => [message];
+}
+
+// Bloc
+class StatusBloc extends Bloc<StatusEvent, StatusState> {
+  final ApiClient apiClient;
+  Timer? _heartbeatTimer;
+
+  StatusBloc({required this.apiClient}) : super(StatusInitial()) {
+    on<StatusLoadRequested>(_onLoad);
+    on<ToggleOnline>(_onToggleOnline);
+    on<ToggleOffline>(_onToggleOffline);
+    on<HeartbeatTick>(_onHeartbeat);
+    on<AppPaused>(_onAppPaused);
+    on<AppResumed>(_onAppResumed);
+  }
+
+  Future<void> _onLoad(StatusLoadRequested event, Emitter<StatusState> emit) async {
+    try {
+      final response = await apiClient.get('/api/mitra/status');
+      final data = response['data'] as Map<String, dynamic>;
+      emit(StatusLoaded(isOnline: data['is_online'] as bool));
+    } catch (e) {
+      emit(StatusLoaded(isOnline: false));
+    }
+  }
+
+  Future<void> _onToggleOnline(ToggleOnline event, Emitter<StatusState> emit) async {
+    emit(StatusLoading());
+    try {
+      await apiClient.post('/api/mitra/status/online');
+      _startHeartbeat();
+      emit(StatusLoaded(isOnline: true));
+    } catch (e) {
+      emit(StatusError('Gagal mengubah status. Coba lagi.'));
+    }
+  }
+
+  Future<void> _onToggleOffline(ToggleOffline event, Emitter<StatusState> emit) async {
+    emit(StatusLoading());
+    try {
+      await apiClient.post('/api/mitra/status/offline');
+      _stopHeartbeat();
+      emit(StatusLoaded(isOnline: false));
+    } catch (e) {
+      emit(StatusError('Gagal mengubah status. Coba lagi.'));
+    }
+  }
+
+  Future<void> _onHeartbeat(HeartbeatTick event, Emitter<StatusState> emit) async {
+    try {
+      await apiClient.post('/api/mitra/status/heartbeat');
+    } catch (_) {
+      // Heartbeat failure is non-critical; server will auto-offline after 45s
+    }
+  }
+
+  Future<void> _onAppPaused(AppPaused event, Emitter<StatusState> emit) async {
+    if (state is StatusLoaded && (state as StatusLoaded).isOnline) {
+      try {
+        await apiClient.post('/api/mitra/status/offline');
+      } catch (_) {}
+      _stopHeartbeat();
+      emit(StatusLoaded(isOnline: false));
+    }
+  }
+
+  Future<void> _onAppResumed(AppResumed event, Emitter<StatusState> emit) async {
+    // Do NOT auto-set online on resume; mitra must explicitly toggle
+    add(StatusLoadRequested());
+  }
+
+  void _startHeartbeat() {
+    _stopHeartbeat();
+    _heartbeatTimer = Timer.periodic(const Duration(seconds: 15), (_) {
+      add(HeartbeatTick());
+    });
+  }
+
+  void _stopHeartbeat() {
+    _heartbeatTimer?.cancel();
+    _heartbeatTimer = null;
+  }
+
+  @override
+  Future<void> close() {
+    _stopHeartbeat();
+    return super.close();
+  }
+}