some backend fixes and add android app

android/core/build.gradle.kts

@@ -0,0 +1,17 @@
+plugins {
+    alias(libs.plugins.kotlin.jvm)
+}
+
+kotlin {
+    jvmToolchain(21)
+}
+
+dependencies {
+    testImplementation(libs.kotlin.test)
+}
+
+tasks.test {
+    testLogging {
+        events("passed", "failed", "skipped")
+    }
+}