chat/media: докачка недостающего медиа после стартовой синхронизации + HAVE_BLOCK анонс локальных блоков

src/utun_instance.c

@@ -478,6 +478,7 @@ void utun_instance_destroy(struct UTUN_INSTANCE *instance) {
 
     /* Phase H: chat */
     chat_headless_control_destroy();
+    chat_media_startup_backfill_destroy(instance);
     chat_sync_destroy(instance);
     chat_core_destroy(instance);
     DEBUG_INFO(DEBUG_CATEGORY_SYS, "[DESTROY] H done — chat");
@@ -663,6 +664,7 @@ int utun_instance_init(struct UTUN_INSTANCE *instance) {
         if (chat_core_init(instance, db_file) == 0) {
             chat_sync_init(instance);
             chat_media_backfill();
+            chat_media_startup_backfill_init(instance);
         }
     }