some backend fixes and add android app

android/build.gradle.kts

@@ -0,0 +1,8 @@
+// Plugins are applied per module; this file only declares them so the version
+// catalog resolves them once for the whole build.
+plugins {
+    alias(libs.plugins.kotlin.jvm) apply false
+    alias(libs.plugins.android.application) apply false
+    alias(libs.plugins.kotlin.compose) apply false
+    alias(libs.plugins.kotlin.serialization) apply false
+}