Convert all projects to PlatformIO

- JC3636W518 sketches: pioarduino 51.03.05 (Arduino core 3.0.5), ESP32-S3
  16MB QIO / OPI PSRAM, vendor libs via lib_extra_dirs, per-project lv_conf.h
- display_gif_embedded uses default_16MB.csv (firmware 3.4 MB > huge_app)
- elm327_wifi_bridge: espressif32 6.10.0 on esp32dev, pinned lib_deps
- elmulator: library in lib/, one env per example, duplicate copies removed
- .ino -> src/main.cpp, headers/lv_conf.h -> include/

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

.gitignore

@@ -0,0 +1,6 @@
+# PlatformIO build output and IDE files
+.pio/
+.vscode/.browse.c_cpp.db*
+.vscode/c_cpp_properties.json
+.vscode/launch.json
+.vscode/ipch