Initial commit: Android Tether API app

Exposes phone connection status via HTTP API for tethered devices.

Features:
- Auto-start/stop server when tethering is enabled/disabled
- REST API with /status and /health endpoints
- Connection type, signal strength, carrier, battery info
- Foreground service with persistent notification

Stack: Kotlin 2.3, AGP 8.13, Gradle 8.13, compileSdk 36

build.gradle.kts

@@ -0,0 +1,4 @@
+plugins {
+    id("com.android.application") version "8.13.0" apply false
+    id("org.jetbrains.kotlin.android") version "2.3.0" apply false
+}