initial

lib/screens/main_shell.dart

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+import 'package:flutter/material.dart';
+import 'devices_screen.dart';
+import 'timbang_screen.dart';
+
+/// Root scaffold with bottom nav: Devices and Timbang (scale display).
+class MainShell extends StatefulWidget {
+  const MainShell({super.key});
+
+  @override
+  State<MainShell> createState() => _MainShellState();
+}
+
+class _MainShellState extends State<MainShell> {
+  int _index = 0;
+
+  static const _tabs = [
+    (label: 'Devices', icon: Icons.list_alt),
+    (label: 'Timbang', icon: Icons.monitor_weight),
+  ];
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: IndexedStack(
+        index: _index,
+        children: const [
+          DevicesScreen(),
+          TimbangScreen(),
+        ],
+      ),
+      bottomNavigationBar: BottomNavigationBar(
+        currentIndex: _index,
+        onTap: (i) => setState(() => _index = i),
+        items: _tabs
+            .map((t) => BottomNavigationBarItem(
+                  icon: Icon(t.icon),
+                  label: t.label,
+                ))
+            .toList(),
+      ),
+    );
+  }
+}