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/Kconfig.projbuild

@@ -0,0 +1,18 @@
+menu "Board indicators"
+
+config BOARD_RGB_LED_ENABLE
+    bool "Turn off onboard addressable RGB at boot (WS2812/SK6812)"
+    default y
+    help
+        ESP32-S3-DevKitC-1 v1.x typically uses one SK6812/WS2812 on GPIO 48.
+        Disable if your board has no addressable LED or uses a different data pin.
+
+config BOARD_RGB_LED_GPIO
+    int "Addressable LED data GPIO"
+    default 48
+    range 0 48
+    depends on BOARD_RGB_LED_ENABLE
+    help
+        Official DevKitC-1 v1.1: GPIO 48. Older notes sometimes cite GPIO 38 — set in menuconfig if needed.
+
+endmenu