Remove arduino-esp32 dependency, modernise WiFi and SPI compat

- Replace Arduino WiFi.h in Networking.cpp with native esp_wifi/esp_netif;
  uses event-driven connect with FreeRTOS EventGroup and 30 s timeout
- Remove initArduino() / Arduino.h from main.cpp
- Remove deprecated arduino-esp32 submodule (was uninitialized and marked
  deprecated since it was first added in Dec 2021)
- rc522.h: guard VSPI_HOST → SPI3_HOST for ESP-IDF 5.x compatibility
- WebInterface.cpp: drop redundant esp_wifi.h (esp_netif.h is sufficient)
- CMakeLists.txt: add esp_wifi + nvs_flash to REQUIRES

https://claude.ai/code/session_01MhAnh68DPNnTjcKqjNYDmk

device/components/esp-idf-rc522/rc522.h

@@ -10,7 +10,12 @@ extern "C" {
 #define RC522_DEFAULT_MOSI                 (23)
 #define RC522_DEFAULT_SCK                  (19)
 #define RC522_DEFAULT_SDA                  (22)
-#define RC522_DEFAULT_SPI_HOST             (VSPI_HOST)
+/* VSPI_HOST was renamed to SPI3_HOST in ESP-IDF 5.0 */
+#ifdef VSPI_HOST
+#  define RC522_DEFAULT_SPI_HOST           (VSPI_HOST)
+#else
+#  define RC522_DEFAULT_SPI_HOST           (SPI3_HOST)
+#endif
 #define RC522_DEFAULT_SCAN_INTERVAL_MS     (125)
 #define RC522_DEFAULT_TACK_STACK_SIZE      (4 * 1024)
 #define RC522_DEFAULT_TACK_STACK_PRIORITY  (4)