new client connection logic

- esp32 requests for image when ready to receive
- server serves initial image on request

components/user_app/user_app.cpp

@@ -200,6 +200,7 @@ static void sensor_task(void *arg)
         if (img_updated && Lvgl_lock(100)) {
             dashboard_ui_update_status_image(img);
             Lvgl_unlock();
+            audio_client_ack_status_image();
         }
 
         /* Sensor + clock updates at ~1s cadence (skip if woken early) */