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

.gitmodules

@@ -1,3 +0,0 @@
-[submodule "device/components/arduino-esp32"]
-	path = device/components/arduino-esp32
-	url = https://github.com/espressif/arduino-esp32.git