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/build.gradle.kts

@@ -0,0 +1,24 @@
+allprojects {
+    repositories {
+        google()
+        mavenCentral()
+    }
+}
+
+val newBuildDir: Directory =
+    rootProject.layout.buildDirectory
+        .dir("../../build")
+        .get()
+rootProject.layout.buildDirectory.value(newBuildDir)
+
+subprojects {
+    val newSubprojectBuildDir: Directory = newBuildDir.dir(project.name)
+    project.layout.buildDirectory.value(newSubprojectBuildDir)
+}
+subprojects {
+    project.evaluationDependsOn(":app")
+}
+
+tasks.register<Delete>("clean") {
+    delete(rootProject.layout.buildDirectory)
+}