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/main/main.c

@@ -0,0 +1,17 @@
+#include "esp_log.h"
+#include "board_rgb_off.h"
+#include "nfc_engine/nfc_engine.h"
+#include "nfc_engine/session_capture.h"
+#include "net_service/app_net.h"
+
+static const char *TAG = "main";
+
+void app_main(void)
+{
+    board_rgb_led_quiet();
+    ESP_LOGI(TAG, "PN532 NFC Toolkit starting");
+    ESP_ERROR_CHECK(nfc_engine_init());
+    session_capture_init();
+    ESP_ERROR_CHECK(app_net_init());
+    ESP_LOGI(TAG, "Open AP SSID PN532-Toolkit — http://192.168.4.1");
+}