Add shared JC3636W518 board library and PlatformIO config

- shared/lib/JC3636W518: display/touch/backlight init with LVGL 9 glue
  (from scr_st77916.h), pin map, perf monitor (FPS/refresh/CPU)
- shared/include/lv_conf.h: LVGL 9.6 config for all projects
- shared/jc3636w518.ini: common platform/board/build settings
- display_gif_embedded uses it (23.2 fps, 86% CPU)

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

shared/lib/JC3636W518/library.json

@@ -0,0 +1,7 @@
+{
+  "name": "JC3636W518",
+  "version": "1.0.0",
+  "description": "Board support for the JC3636W518 (ESP32-S3, ST77916 360x360 QSPI LCD, CST816S touch) with LVGL 9 glue and a performance monitor",
+  "frameworks": "arduino",
+  "platforms": "espressif32"
+}