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/lib/services/session.dart

@@ -0,0 +1,35 @@
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+
+const _kBase = 'odoo_base';
+const _kDb = 'odoo_db';
+const _kUser = 'odoo_user';
+const _kPass = 'odoo_pass';
+
+/// Menyimpan konfigurasi login (url, db, user, password) secara aman
+/// + menyediakan OdooClient terautentikasi.
+class Session {
+  static const _storage = FlutterSecureStorage();
+
+  static Future<void> save(String baseUrl, String db, String user, String pass) async {
+    await _storage.write(key: _kBase, value: baseUrl);
+    await _storage.write(key: _kDb, value: db);
+    await _storage.write(key: _kUser, value: user);
+    await _storage.write(key: _kPass, value: pass);
+  }
+
+  static Future<({String base, String db, String user, String pass})?> load() async {
+    final base = await _storage.read(key: _kBase);
+    final db = await _storage.read(key: _kDb);
+    final user = await _storage.read(key: _kUser);
+    final pass = await _storage.read(key: _kPass);
+    if (base == null || user == null || pass == null) return null;
+    return (base: base, db: db ?? 'odoo', user: user, pass: pass);
+  }
+
+  static Future<void> clear() async {
+    await _storage.delete(key: _kBase);
+    await _storage.delete(key: _kDb);
+    await _storage.delete(key: _kUser);
+    await _storage.delete(key: _kPass);
+  }
+}