android(call): Increment 2a — native LiveKit call audio, background service, speaker/BT routing

Replaces WebView call media on Android with a native LiveKit connection (iOS
parity), so call audio survives backgrounding and the output can be switched
to Speaker/Bluetooth/Earpiece — the #3 (missing speaker control) and #4
(background audio) items.

Gated behind a new, default-off server flag ANDROID_NATIVE_MEDIA (independent
of ANDROID_CALLS, which only governs the native ring). Flag off = today's
WebView media, video included; flag on = native audio (video is Increment 2b,
so enable it for VOICE testing first). No behavior change until flipped.

Native (mobile/plugins/native-call/android):
- build.gradle: add kotlin-android + io.livekit:livekit-android 2.29.2 (+ twilio
  audioswitch, coroutines) + JitPack repo; minSdk 24 (LiveKit floor).
- CallMedia.kt: LiveKit Room wrapper — connect/mic/disconnect + AudioSwitchHandler
  routing (auto + selectDevice) and route-change events.
- CallForegroundService.java: microphone-type foreground service for background
  audio (no-ops without RECORD_AUDIO so it never crashes the call).
- NativeCallPlugin.java: real bodies for reportOutgoingCall/reconnectRoom/setMuted
  /endCall + new setAudioRoute/getAudioRoute; fires callConnected/callError/audioRoute.
- AndroidManifest: FG service + FOREGROUND_SERVICE(_MICROPHONE)/RECORD_AUDIO/
  MODIFY_AUDIO_SETTINGS/BLUETOOTH_CONNECT.
- android-patch.js: bump the generated app minSdk to 24.

Server:
- config.js/routes.js: ANDROID_NATIVE_MEDIA → /api/meetings/config.androidNativeMedia.

Web (home.html):
- Android flips to the native-media path when androidNativeMedia is set; the
  existing outgoing/answer/mic/end code then drives the plugin unchanged.
- Speaker button wired for Android native: cycles speaker/earpiece/bluetooth via
  NC.setAudioRoute and reflects the real output from the audioRoute event.

Video stays no-op on the native path (Increment 2b).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/config.js

@@ -55,6 +55,14 @@ const CALLKIT_ENABLED = process.env.CALLKIT_ENABLED === '1';
 // FCM configured (FCM_SERVICE_ACCOUNT) + an app build carrying the native-call Android plugin. Set ANDROID_CALLS=1.
 const ANDROID_CALLS = process.env.ANDROID_CALLS === '1';
 
+// Native call MEDIA on Android (Increment 2): LiveKit audio in the plugin + a foreground service, instead of the
+// WebView carrying the media. INDEPENDENT of ANDROID_CALLS (which only governs the native ring) so media can be
+// flipped on for testing after the ring is solid. OFF (default) → Android keeps WebView call media (works today,
+// video included). ON → the Android app drives call audio natively (background audio + Speaker/Bluetooth), but
+// video is not yet native (Increment 2b) — so enable this for VOICE testing first. Requires an app build carrying
+// the LiveKit-Android plugin. Set ANDROID_NATIVE_MEDIA=1.
+const ANDROID_NATIVE_MEDIA = process.env.ANDROID_NATIVE_MEDIA === '1';
+
 module.exports = {
   PORT: process.env.PORT || 8090,
   HTTPS_PORT: process.env.HTTPS_PORT || 8443,
@@ -73,6 +81,7 @@ module.exports = {
   GIPHY_API_KEY,
   CALLKIT_ENABLED,
   ANDROID_CALLS,
+  ANDROID_NATIVE_MEDIA,
   PUBLIC_DIR,
   REC_DIR,
   TRANS_DIR,