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/features/chat/widgets/incoming_request_sheet.dart

@@ -0,0 +1,55 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import '../../../core/chat/chat_request_bloc.dart';
+
+class IncomingRequestSheet extends StatelessWidget {
+  final String sessionId;
+  const IncomingRequestSheet({super.key, required this.sessionId});
+
+  @override
+  Widget build(BuildContext context) {
+    return Container(
+      padding: const EdgeInsets.all(24),
+      child: Column(
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          const Icon(Icons.chat, size: 48, color: Colors.blue),
+          const SizedBox(height: 16),
+          const Text(
+            'Ada permintaan chat baru!',
+            style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold),
+          ),
+          const SizedBox(height: 8),
+          const Text(
+            'Seorang customer ingin curhat denganmu.',
+            style: TextStyle(fontSize: 14, color: Colors.grey),
+          ),
+          const SizedBox(height: 24),
+          Row(
+            children: [
+              Expanded(
+                child: OutlinedButton(
+                  onPressed: () {
+                    context.read<ChatRequestBloc>().add(DeclineRequest(sessionId));
+                    Navigator.of(context).pop();
+                  },
+                  child: const Text('Tolak'),
+                ),
+              ),
+              const SizedBox(width: 16),
+              Expanded(
+                child: ElevatedButton(
+                  onPressed: () {
+                    context.read<ChatRequestBloc>().add(AcceptRequest(sessionId));
+                    Navigator.of(context).pop();
+                  },
+                  child: const Text('Terima'),
+                ),
+              ),
+            ],
+          ),
+        ],
+      ),
+    );
+  }
+}