call: P2P аудиозвонки — сигналинг, релей медиа, аудио-контур, headless/desktop/android

- src/call/: сигналинг (call.c, call_proto.h, ETCP_RT_ID_CALL 0x36) + релей медиа
  + headless аудио-сокет (call_headless.c, call_audio_bind) + Opus/jitter/тоны
- chat: события CHAT_EVT_CALL_* (34–40), CHAT_EVT_DM_MESSAGES (41), DM-трамплины
- chatgui: call window, miniaudio I/O, audio_frame_ring, test_audio_jitter
- chatgui-android: CallScreen/IncomingCallDialog, аудио-роутинг, JNI, рингтон
- tests: test_call, test_call_headless

src/utun_instance.h

@@ -39,6 +39,7 @@ struct chat_sync;
 struct join_key_entry;   /* chat_join.c */
 struct dm_state;
 struct dm_mb_state;
+struct call_ctx;         /* call/call.c */
 struct uasync_s;
 struct ROUTE_TABLE;
 struct ETCP_CONN;
@@ -199,6 +200,8 @@ struct UTUN_INSTANCE {
     struct join_key_entry* join_keys;     // chat_join.c (was g_keys; собственный init/destroy)
     struct dm_state*      dm;             // dm/dm_core.c (was g_dm)
     struct dm_mb_state*   dm_mailbox;     // dm/dm_mailbox.c (was g_mb)
+    struct call_ctx*      call;           // call/call.c — P2P audio call
+    void*                 call_audio;     // call/call_headless.c — audio stream socket
     struct chat_setting_state chat_settings;  // chat_setting.c (was globals)
     chat_event_handler_fn chat_event_handler;  // chat_event.c (was g_handler)
     void*                 headless;       // chat_headless_control.c (was g_hc)