Add per-slave ESP-NOW OTA progress over UART and fix dashboard updates.

Expose OTA_SLAVE_PROGRESS on the master, track per-slave state during
distribution, run ESP-NOW OTA in a background task so the host can poll
while slaves update, and show master/slave progress in the dashboard
with table layout and faster WebSocket refresh during uploads.

Co-authored-by: Cursor <cursoragent@cursor.com>

main/powerpod.c

@@ -5,6 +5,7 @@
 #include "cmd_client_info.h"
 #include "cmd_version.h"
 #include "cmd_ota.h"
+#include "cmd_ota_slave_progress.h"
 #include "esp_now_comm.h"
 #include "powerpod.h"
 #include "driver/gpio.h"
@@ -168,6 +169,7 @@ void app_main(void) {
     cmd_accel_deadzone_register();
     cmd_espnow_unicast_test_register();
     cmd_ota_register();
+    cmd_ota_slave_progress_register();
   }
 
   uint8_t current_digit = 10;