android: fix key regeneration, Clear DB, uasync eventfd, udp log from config

- jni_on_event: fix JNI_EDETACHED — AttachCurrentThread/DetachCurrentThread
- u_async.c: pipe→eventfd for reliable cross-thread wakeup
  add process_posted_tasks in poll() path, fix EINTR (saved_errno)
- bridge_debug_hook: keep udp_log_write, remove mutex from udp_log
- memory_pool.c: alloc/free logs INFO→DEBUG (reduce spam)
- instance_lite.c: chat_event_set_handler before ensure_keys,
  KEYS_GENERATED events, fchmod 0600 on keys.conf,
  UDP log from config [log_udp] section, regenerate_trampoline
- config_parser: parse [log_udp] ip/port
- NativeLib.kt: remove callbacksSet, simplify init/stop/destroy
- ChatViewModel.kt: unified event callback in init, pubKey StateFlow,
  requestRegenerateKeys, clearState fix
- SettingsScreen.kt: pubKey.collectAsState(), Clear DB via restart()
- HeadlessService.kt: remove setUdpLogTarget (now from config)
- android_udp_log.c: simplified — no mutex, buffer+send+timer in one thread
- utun_instance.c: NULL-check tcp_connections before destroy
- chat_event.h: +CHAT_EVT_KEYS_GENERATED 11, -NODE_CHANGED
- logreceiver: UDP log receiver tool

src/config_parser.h

@@ -120,6 +120,9 @@ struct global_config {
     char db_path[256];         // Path to SQLite database (empty = disabled)
     int  db_sync_enabled;      // 1 = enable distributed DB sync (default: 0)
     uint32_t db_sync_ttl;      // TTL for unsent records in seconds (default: 86400)
+    // UDP log target
+    char     log_udp_ip[64];
+    int      log_udp_port;
     char debug_level[16];      // debug level: error, warn, info, debug, trace
     int enable_timestamp;      // enable timestamps in logs
     int enable_function_names; // enable function names in logs