Add PN532 toolkit firmware, web UI, and embedded SPIFFS assets

Includes ESP-IDF NFC stack (deep capture, 4K Classic geometry, UL write API,
open SoftAP), React dashboard with live tag diagnostics, and docs. README
updated for APIs and lab Wi-Fi defaults.

Made-with: Cursor

firmware/components/net_service/include/net_service/app_net.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#include "esp_err.h"
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+esp_err_t app_net_init(void);
+void app_net_set_continuous_scan(bool on);
+bool app_net_continuous_scan(void);
+esp_err_t app_net_broadcast_json(const char *channel, const char *json_text);
+
+#ifdef __cplusplus
+}
+#endif