Vendor esp-idf-rc522 as plain source instead of submodule

The library is modified (NDEF reading, cascade anticollision) so vendoring
it directly avoids needing push access to the upstream fork.

https://claude.ai/code/session_01MhAnh68DPNnTjcKqjNYDmk

.gitmodules

@@ -1,7 +1,3 @@
-[submodule "device/components/esp-idf-rc522"]
-	path = device/components/esp-idf-rc522
-	url = https://github.com/sweidac/esp-idf-rc522.git
-
 [submodule "device/components/arduino-esp32"]
 	path = device/components/arduino-esp32
 	url = https://github.com/espressif/arduino-esp32.git