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.

app/build.gradle.kts

@@ -0,0 +1,50 @@
+plugins {
+    id("com.android.application") version "8.4.0"
+    id("org.jetbrains.kotlin.android") version "1.9.22"
+}
+
+android {
+    namespace = "com.fnregistry.unibus"
+    compileSdk = 34
+
+    defaultConfig {
+        applicationId = "com.fnregistry.unibus"
+        minSdk = 24
+        targetSdk = 34
+        versionCode = 1
+        versionName = "0.1.0"
+    }
+
+    buildFeatures {
+        compose = true
+    }
+    composeOptions {
+        kotlinCompilerExtensionVersion = "1.5.8"
+    }
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+    kotlinOptions {
+        jvmTarget = "17"
+    }
+}
+
+dependencies {
+    // unibus client compiled from Go via gomobile: holds the NATS data-plane
+    // connection, the HTTP control-plane calls and the end-to-end crypto. This is
+    // the same pkg/client every other peer uses, so the protocol has one source
+    // of truth.
+    implementation(files("libs/unibus.aar"))
+
+    implementation("androidx.activity:activity-compose:1.8.2")
+    implementation(platform("androidx.compose:compose-bom:2024.02.00"))
+    implementation("androidx.compose.ui:ui")
+    implementation("androidx.compose.material3:material3")
+    implementation("androidx.compose.ui:ui-tooling-preview")
+    debugImplementation("androidx.compose.ui:ui-tooling")
+    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.3")
+
+    // FnTheme + FnTokens via composite build
+    implementation("fn.compose:ui")
+}