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/android/app/src/main/res/drawable-v21/launch_background.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Modify this file to customize your launch splash screen -->
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:drawable="?android:colorBackground" />
+
+    <!-- You can insert your own image assets here -->
+    <!-- <item>
+        <bitmap
+            android:gravity="center"
+            android:src="@mipmap/launch_image" />
+    </item> -->
+</layer-list>