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>

12-OBD-Speed/platformio.ini

@@ -0,0 +1,18 @@
+; OBD speed display: ELM327 over BLE, GIF background, swipe-left menu to pick/remember the adapter.
+; JC3636W518, common settings in shared/jc3636w518.ini
+
+[platformio]
+extra_configs = ../shared/jc3636w518.ini
+
+[shared]
+dir = ../shared
+
+[env:jc3636w518]
+extends = jc3636w518
+; firmware + 1.6 MB background GIF does not fit huge_app (3 MB): 6.25 MB app slots
+board_build.partitions = default_16MB.csv
+; background GIF linked into the firmware as-is (symbols _binary_data_bg_gif_start/_end)
+board_build.embed_files = data/bg.gif
+lib_deps =
+    ${jc3636w518.lib_deps}
+    h2zero/NimBLE-Arduino@2.5.1