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>

client_app/lib/features/chat/screens/bestie_found_screen.dart

@@ -0,0 +1,52 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:go_router/go_router.dart';
+import '../../../core/pairing/pairing_bloc.dart';
+
+class BestieFoundScreen extends StatelessWidget {
+  final String sessionId;
+  final String mitraName;
+
+  const BestieFoundScreen({
+    super.key,
+    required this.sessionId,
+    required this.mitraName,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return BlocListener<PairingBloc, PairingState>(
+      listener: (context, state) {
+        if (state is PairingActive) {
+          context.go('/chat/session/${state.sessionId}', extra: state.mitraName);
+        }
+      },
+      child: Scaffold(
+        body: Center(
+          child: Padding(
+            padding: const EdgeInsets.all(32),
+            child: Column(
+              mainAxisAlignment: MainAxisAlignment.center,
+              children: [
+                const Icon(Icons.check_circle, size: 80, color: Colors.green),
+                const SizedBox(height: 24),
+                const Text(
+                  'Bestie ditemukan!',
+                  style: TextStyle(fontSize: 24, fontWeight: FontWeight.bold),
+                ),
+                const SizedBox(height: 8),
+                Text(
+                  'Menghubungkan kamu ke $mitraName',
+                  textAlign: TextAlign.center,
+                  style: const TextStyle(fontSize: 16, color: Colors.grey),
+                ),
+                const SizedBox(height: 24),
+                const CircularProgressIndicator(),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}