Add 12-OBD-Speed: ELM327 speed over BLE on a GIF background

- speed page: 120 px antialiased number (lv_font_conv) + 0-200 km/h arc
  gauge over ezgif-5-cb56986bc7.gif (embedded via board_build.embed_files)
- swipe-left menu: scan, OBD-like adapters first, tap to select; adapter
  remembered in NVS, auto-connect at boot and reconnect every 3 s
- ELM327 init ATZ/ATE0/ATL0/ATS0/ATH0/ATSP0/0100, then 010D polling
- shared ini: -DLV_LVGL_H_INCLUDE_SIMPLE for generated fonts

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

shared/jc3636w518.ini

@@ -28,6 +28,8 @@ build_flags =
     -DARDUINO_USB_CDC_ON_BOOT=1
     ; LVGL (also when compiled as a library) uses shared/include/lv_conf.h
     -DLV_CONF_INCLUDE_SIMPLE
+    ; generated LVGL fonts/images include "lvgl.h" directly
+    -DLV_LVGL_H_INCLUDE_SIMPLE
     -I${shared.dir}/include
 
 ; shared/lib: JC3636W518 board library