android: real utun instance + SQLite channels + reactive logs + QR join

- instance_lite.h/c: full uTun stack from INI config text
  (keygen, uasync, UTUN_INSTANCE, SQLite, chat_core/sync, BGP, etcp_router)
- jni_bridge: nativeStart/Stop, nativeJoinChannel → chat_sync_connect_from_invite,
  nativeSubscribeLogs, C logs → logcat + Kotlin LogManager
- Kotlin: direct read-only SQLite queries (channels, messages),
  ViewModel with live event callbacks, reactive LogScreen (tail -f),
  CameraX QR scanner with proper lifecycle, JoinChannelDialog
- HeadlessService: generates INI config from Kotlin settings → C instance

lib/debug_config.c

@@ -210,6 +210,7 @@ const char* debug_get_category_name(debug_category_t category_idx) {
 
 /* Global debug configuration */
 debug_config_t g_debug_config;
+static debug_log_hook_fn g_log_hook = NULL;
 
 /* Initialize debug system with default settings */
 void debug_config_init(void) {
@@ -433,6 +434,12 @@ void debug_output(debug_level_t level, debug_category_t category_idx,
     
     va_end(args);
     
+    /* Route to external hook (JNI bridge, etc.) */
+    if (g_log_hook) {
+        const char* cat_name = debug_get_category_name(category_idx);
+        g_log_hook((int)level, cat_name, buffer);
+    }
+    
     /* Output to console if enabled and level is sufficient */
     if (g_debug_config.file_output) {
         fprintf(g_debug_config.file_output, "%s", buffer);
@@ -444,6 +451,10 @@ void debug_output(debug_level_t level, debug_category_t category_idx,
 #undef BUFFER_SIZE
 }
 
+void debug_set_log_hook(debug_log_hook_fn hook) {
+    g_log_hook = hook;
+}
+
 /* Parse debug configuration from string (e.g., "ll_queue:debug,uasync:info,memory:warn,etcp:error") */
 int debug_parse_config(const char* config_string) {
     if (!config_string || !*config_string) {