dm: прямой обмен сообщениями (DM) + soundtouch + архитектура звонков

- src/dm/: dm_core/dm_crypto/dm_mailbox — прямой обмен сообщениями (DM)
- lib/soundtouch-master/: vendored SoundTouch (изменение темпа/высоты аудио)
- doc/dm_arch.md, doc/chat_call_arch.md: архитектура DM и звонков
- tests: test_dm.c, test_dm_e2e.c
- chat: рефакторинг chat_* модулей, member_sync, invite_build
- chatgui/chatgui-android: синхронизация с новым API чата
- lib/u_async, debug_config, utun_instance: сопутствующие изменения

src/utun_instance.h

@@ -29,9 +29,16 @@ extern "C" {
 #include "etcp_api.h"
 #include "config_parser.h"
 #include "topo_group.h"
+#include "chat/chat_setting.h"
+#include "chat/chat_event.h"
 
 // Forward declarations
 struct utun_config;
+struct chat_core_ctx;
+struct chat_sync;
+struct join_key_entry;   /* chat_join.c */
+struct dm_state;
+struct dm_mb_state;
 struct uasync_s;
 struct ROUTE_TABLE;
 struct ETCP_CONN;
@@ -186,6 +193,16 @@ struct UTUN_INSTANCE {
     struct CONN_MGR* conn_mgr;       // Connection Manager (может быть NULL)
     struct DB_SYNC* db_sync;         // Distributed DB sync (может быть NULL)
 
+    // Chat/DM subsystem (per-instance contexts; were global singletons)
+    struct chat_core_ctx* chat_core;      // chat_core.c (was g_cc)
+    struct chat_sync*     chat_sync;      // chat_sync.c (was g_cs)
+    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 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)
+
     // E2E encryption cache — per-peer sc_context_t with derived session key
 #define E2E_CTX_CACHE_SIZE 8
     struct { uint64_t peer_node_id; struct secure_channel ctx; uint8_t valid; } e2e_ctx_cache[E2E_CTX_CACHE_SIZE];