Scaffold native Android build and enforce Rust boundaries (#89)

android/gradle.properties

@@ -0,0 +1,8 @@
+org.gradle.jvmargs=-Xmx4g -Dfile.encoding=UTF-8
+org.gradle.parallel=true
+org.gradle.caching=true
+org.gradle.configuration-cache=true
+org.gradle.java.installations.auto-download=false
+android.injected.androidTest.leaveApksInstalledAfterRun=true
+android.useAndroidX=true
+kotlin.code.style=official