feat: Android Compose client for the unibus bus

Thin Jetpack Compose UI over the real Go client (pkg/client) compiled to a
gomobile .aar, so the phone speaks NATS and runs the same end-to-end crypto as
any other peer. Connect, create room (nats/matrix), publish and live-receive.

build.gradle.kts

@@ -0,0 +1,5 @@
+// Top-level build file where you can add configuration options common to all sub-projects/modules.
+plugins {
+    id("com.android.application") version "8.4.0" apply false
+    id("org.jetbrains.kotlin.android") version "1.9.22" apply false
+}