Phase 3: hide mitra force-close (Akhiri) button in active sessions

Removes the Akhiri button + confirmation dialog + _endSession from the
mitra active sessions screen. Backend POST .../end-early route and the
early_end_mitra_enabled config flag are preserved — re-enable plan lives
in requirement/phase3.6.md.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

mitra_app/lib/features/chat/screens/active_sessions_screen.dart

@@ -33,34 +33,6 @@ class _ActiveSessionsScreenState extends ConsumerState<ActiveSessionsScreen> {
     }
   }
 
-  Future<void> _endSession(String sessionId) async {
-    final confirmed = await showDialog<bool>(
-      context: context,
-      builder: (ctx) => AlertDialog(
-        title: const Text('Akhiri Sesi?'),
-        content: const Text('Apakah kamu yakin ingin mengakhiri sesi ini?'),
-        actions: [
-          TextButton(onPressed: () => Navigator.of(ctx).pop(false), child: const Text('Batal')),
-          TextButton(onPressed: () => Navigator.of(ctx).pop(true), child: const Text('Ya, Akhiri')),
-        ],
-      ),
-    );
-
-    if (confirmed == true) {
-      try {
-        final apiClient = ref.read(apiClientProvider);
-        await apiClient.post('/api/mitra/chat-requests/sessions/$sessionId/end');
-        _loadSessions();
-      } catch (_) {
-        if (mounted) {
-          ScaffoldMessenger.of(context).showSnackBar(
-            const SnackBar(content: Text('Gagal mengakhiri sesi.')),
-          );
-        }
-      }
-    }
-  }
-
   @override
   Widget build(BuildContext context) {
     return Scaffold(
@@ -78,10 +50,7 @@ class _ActiveSessionsScreenState extends ConsumerState<ActiveSessionsScreen> {
                       leading: const Icon(Icons.chat),
                       title: Text(customerName),
                       subtitle: Text('Status: ${session['status']}'),
-                      trailing: TextButton(
-                        onPressed: () => _endSession(session['id'] as String),
-                        child: const Text('Akhiri', style: TextStyle(color: Colors.red)),
-                      ),
+                      trailing: const Icon(Icons.chevron_right),
                       onTap: () => context.push(
                         '/chat/session/${session['id']}',
                         extra: {'customerName': customerName},