Add Opencode (opencode.ai) integration via SSH tunnel

Features:
- Opencode AI chat interface
- SSH tunnel for secure API communication
- Auto-install Opencode on remote servers
- API key management with server-side storage
- Session history and management
- Integration with flutter_server_box server list

lib/view/widget/server_func_btns.dart

@@ -212,6 +212,10 @@ void _onTapMoreBtns(ServerFuncBtn value, Spi spi, BuildContext context, WidgetRe
       final args = SpiRequiredArgs(spi);
       PortForwardPage.route.go(context, args);
       break;
+    case ServerFuncBtn.opencode:
+      // Opencode AI Assistant
+      context.push('/opencode/setup/${spi.id}');
+      break;
   }
 }