Initial implementation of BLE-to-TCP serial bridge for Android

Android app that connects to a BLE UART device (Nordic UART Service by
default, matching RNode BLE) and exposes it as a TCP byte pipe, so socat
can present it to Reticulum as a serial port. Foreground service hosts a
GATT client with MTU negotiation, chunked serialized writes, and
auto-reconnect, plus a single-client last-wins TCP server. No root
required on either end.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

build.gradle.kts

@@ -0,0 +1,4 @@
+plugins {
+    id("com.android.application") version "8.13.0" apply false
+    id("org.jetbrains.kotlin.android") version "2.2.20" apply false
+}