Gabung app Android Flutter 'Saat Invest' ke repo saat-app (folder flutter/)

Satu repo untuk backend Odoo (addon saat_invest) + app Android.
- flutter/ berisi project Flutter (lib/, android/, pubspec, test)
- Login Odoo JSON-RPC, tab Portofolio+Equity, tab Transaksi, catat jual/beli otomatis sync
- Build .gitignore nested dipakai sehingga artefak build/.dart_tool tak ter-track
Sejarah: gabung flat (satu sejarah backend+app).

flutter/test/widget_test.dart

@@ -0,0 +1,13 @@
+// Smoke test: aplikasi bisa dibangun & menampilkan layer login (tanpa session,
+// RootScreen saat load akan menampilkan LoginScreen karena tidak ada cred).
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:saat_invest_mobile/main.dart';
+
+void main() {
+  testWidgets('App boot shows Saat Invest login', (tester) async {
+    await tester.pumpWidget(const SaatInvestApp());
+    await tester.pumpAndSettle();
+    expect(find.text('Masuk'), findsOneWidget);
+  });
+}