Add ESP-NOW master/slave discovery on DIP network channel.

Initialize WiFi and ESP-NOW from shared app config; master broadcasts
discover packets and collects slave info, slaves respond on matching
network while UART commands stay master-only.

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

main/esp_now_comm.h

@@ -0,0 +1,9 @@
+#ifndef ESP_NOW_COMM_H
+#define ESP_NOW_COMM_H
+
+#include "app_config.h"
+#include "esp_err.h"
+
+esp_err_t esp_now_comm_init(const app_config_t *config);
+
+#endif