Keep the Android connection alive in the background

The session moves from the connection screen's ViewModel into an
app-wide SessionController, and a foreground service keeps the process
running while connected:

- Its notification shows the server and status and offers Mute, Deafen
  and Disconnect.
- It declares microphone use only once the microphone is handed to the
  connection, as Android requires that permission to be granted then.
- It holds a low-latency Wi-Fi lock and a CPU wake lock, since voice
  goes out every 20 ms.
- When the system moves to another network, the session reconnects to
  where it was, as its socket stays bound to the old one.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

android/app/src/main/res/values/strings.xml

@@ -1,4 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
     <string name="app_name">TS3J</string>
+    <string name="connection_channel">Connection</string>
 </resources>