[Fix] Prevent use-after-free in Redis callbacks after session cleanup

Set ud->terminated in lua_redis_fin() so async Redis callbacks
don't access task data after the task pool has been freed.

src/lua/lua_redis.c

@@ -272,6 +272,8 @@ lua_redis_fin(void *arg)
 	msg_debug_lua_redis("finished redis query %p from session %p; refcount=%d",
 						sp_ud, ctx, ctx->ref.refcount);
 	sp_ud->flags |= LUA_REDIS_SPECIFIC_FINISHED;
+	/* Prevent callbacks from accessing task data after session cleanup */
+	ud->terminated = 1;
 
 	REDIS_RELEASE(ctx);
 }